| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Cholesterol metabolism in the rat lactating mammary gland: the role of cholesteryl ester hydrolase Botham, K. M. (1991), Lipids 26(11): 901-6. Abstract: An acid cholesteryl ester hydrolase activity associated with a fraction containing mitochondria and lysosomes from rat lactating mammary glands was found to have a pH optimum of 5.0. Its sedimentation pattern was closely related to that of the lysosomal enzyme markers acid phosphatase and beta-glucuronidase, suggesting that the activity is associated with the lysosomes. The enzyme was strongly inhibited by Cu2+, but was inhibited little by other divalent metal ions. Acid cholesteryl ester hydrolase activity was almost completely abolished by p-hydroxy-mercuribenzoate, but this effect was reversed in the presence of an equimolar concentration of reduced glutathione (GSH), indicating that the enzyme requires free sulfhydryl groups for activity. These properties are similar to those of acid, lysosomal cholesteryl ester hydrolases found in other tissues. Acid cholesteryl ester hydrolase activity was 8-14 fold higher in mammary tissue from lactating as compared to virgin rats. Neutral cholesteryl ester hydrolase activities associated with the microsomal and cytosolic subcellular fractions were also increased in lactating glands, but to a lesser extent. In addition, a 2-fold increase in the activities of both the acid and microsomal neutral enzymes was seen during the first few days of lactation, while the cytosolic neutral activity remained constant. These results suggest that mammary gland cholesteryl ester hydrolases have a role in the regulation of cholesterol metabolism in mammary cells, and in the provision of cholesterol for secretion into milk. |
| Cholesterol metabolism in the RSH/Smith-Lemli-Opitz syndrome: summary of an NICHD conference Opitz, J. M. and F. de la Cruz (1994), Am J Med Genet 50(4): 326-38. Abstract: During the evolution of multicellularity and attendant processes of development, cholesterol played a key role in the formation of the plasma membrane and outer mitochondrial membrane of every cell in the organism. Later functions include pivotal involvement in steroid, bile acid, and vitamin D metabolism and myelination of the nervous system. In the CNS myelination does not begin until the third trimester, and subcortical myelination not until after birth. The cholesterol of the cell membrane of the ovum is maternally derived. It is not known when the zygote begins making its own cholesterol during morphogenesis and histogenesis, but it must occur early to keep up with the dramatic rate of cell division in the embryo. Thus, it is a startling surprise that human embryos and fetuses apparently able to synthesize little cholesterol (because of a presumed defect of the delta 5,7-sterol, delta 7-reductase that converts 7-dehydrocholesterol (7-DHC) into cholesterol) frequently live to term and, rarely, may be so mildly affected as to attend school with only mild MR. The discovery by G. Stephen Tint and his co-workers of the apparent 7-DHC reductase deficiency makes the RSH (Smith-Lemli-Opitz) syndrome the first true metabolic malformation syndrome. A teratological animal model which has been known for 30 years now appears applicable to the RSH/SLO syndrome. A multidisciplinary NICHD conference held on September 20-21, 1993 reviewed the numerous implications of this discovery and agreed unanimously that research in this field be given highest priority in order to better understand cholesterol synthesis in the mammalian brain, cholesterol transport from mother to embryo and fetus, pre- and postnatal metabolic compensation in structure and function for a profound block in cholesterol synthesis, the nature of the blood-brain barrier for cholesterol, treatment of affected infants, children, and adults, structure and genetic specification of a 7-DHC reductase enzyme (which has never been purified!) and its evolution, the variability of the syndrome and whether it is genetically homo- or heterogeneous, the population genetics of the RSH syndrome, possible selective advantages (or disadvantages) of heterozygotes, and means of newborn screening, carrier detection, and prenatal diagnosis. |
| Cholesterol metabolism in type 1 diabetes Gylling, H., J. A. Tuominen, et al. (2004), Diabetes 53(9): 2217-22. Abstract: Little information is available on cholesterol absorption and synthesis in human type 1 diabetes. We studied these variables using serum cholesterol precursor sterol ratios to cholesterol as surrogate markers of cholesterol synthesis and those of cholestanol and plant sterols to reflect cholesterol absorption in seven type 1 diabetic subjects and in five age- and body weight-matched control subjects. Total and lipoprotein cholesterol levels were similar, but triglycerides in intermediate-density lipoprotein (IDL) and LDL were higher in type 1 diabetic than in control subjects. Most of the marker sterols were transported by LDL and HDL in both groups. The percentage of esterified cholesterol was lower in triglyceride-rich lipoproteins in diabetic patients than in control subjects. The ratios of the absorption marker sterols in serum were higher, and those of the synthesis markers were lower in type 1 diabetic than in control subjects. The increased cholestanol ratios were seen in all lipoproteins, and those of free and total plant sterols were mainly in LDL, whereas the decreased free and total synthesis markers were mainly in all lipoproteins. In conclusion, high absorption and low synthesis marker sterols seem to characterize human type 1 diabetes. These findings could be related to low expression of ABC G/5 G/8 genes, resulting in high absorption of cholesterol and sterols in general and low synthesis of cholesterol compared with type 2 diabetes. |
| Cholesterol metabolism is affected by calcium phosphate supplementation in humans Ditscheid, B., S. Keller, et al. (2005), J Nutr 135(7): 1678-82. Abstract: Dietary calcium and phosphate precipitate in the small intestine to form insoluble amorphous calcium phosphate (ACP). The ability of ACP to bind and inactivate luminal bile acids might have an effect on cholesterol metabolism. To test this hypothesis, a placebo-controlled, double-blind, crossover study with pentacalcium hydroxy-triphosphate supplementation (CaP; 1.0 g elemental calcium) was conducted in 31 young healthy volunteers. The CaP was incorporated into bread. Serum cholesterol concentrations were lower after 4 wk of supplementation than after 4 wk of placebo (4.36 vs. 4.60 mmol/L; P = 0.008). Serum LDL cholesterol and the ratio of LDL:HDL cholesterol also tended to be lower after CaP supplementation than after placebo (-5.6%, P = 0.083 and -5.4%, P < 0.062, respectively). The participants' fat and cholesterol intakes and fecal fat excretion did not differ in the 2 periods. Although the analysis of fecal samples showed no difference in the excretion of total neutral sterols (sum of cholesterol and its transformation products), the excretion of cholesterol itself increased (9.64 vs. 5.80 micromol/g dry matter; P = 0.025; n = 25), whereas the excretion of the metabolite coprostanol decreased (18.5 vs. 21.0 mumol/g dry matter; P = 0.025; n = 25) in the CaP period. Bile acid excretion increased during the CaP period compared with the placebo period (25.4 vs. 22.9 micromol/g dry matter; P = 0.003). The observed beneficial effects on cholesterol metabolism are not the result of an increased excretion of cholesterol, but might be explained by an increased bile acid excretion and a subsequent regeneration of bile acids from endogenous cholesterol in the liver. |
| Cholesterol metabolism is altered when rats are fed either beef tallow as the only dietary fat or fat containing the lipid extracts of beef O'Brien, B. C. (1994), J Nutr 124(7): 1112-7. Abstract: This study was designed to evaluate tissue cholesterol concentrations in rats fed the nonpolar component or the polar component of the lipid extracted from beef. Comparisons were made to tissue cholesterol concentrations of rats fed either whole beef or beef tallow. The nonpolar component was predominantly triacylglycerol with a fatty acid composition similar to that of the beef tallow. Rats consuming the diet containing the nonpolar component had a plasma cholesterol concentration similar to those of rats in the other treatment groups. However, their plasma HDL cholesterol concentration was significantly greater and their hepatic cholesterol concentration was significantly less than for rats fed the diet with beef tallow but not rats fed the diet with beef or the polar component of beef lipid. Rats fed the diet with the polar component had a plasma cholesterol concentration that was significantly less than that of the beef tallow-fed group but similar to those of the other treatment groups; however, their plasma HDL cholesterol concentration was not different from that of any other group. Comparing electrophoretic lipoprotein profiles among diet groups demonstrated enhanced proportions of HDL in rats fed beef or the nonpolar component rather than beef tallow. These data suggest a novel effect of endogenous nonpolar beef lipid on cholesterol metabolism, which seems to depend upon factor(s) other than properties that are similar to the properties of beef tallow, i.e., fatty acid composition and lipid polarity. |
| Cholesterol metabolism modulators and the future of atherosclerosis therapy Morozova, S., I. Suc-Royer, et al. (2004), Med Sci (Paris) 20(6-7): 685-90. Abstract: Atherosclerosis is a disease characterized by lipid accumulation in the vascular wall leading to myocardial infarction or stroke. Hypercholesterolemia is an important risk factor and current treatments are largely based on cholesterol lowering. In spite of proven efficacy of existing drugs, like statins, cardiovascular diseases still remain the most common cause of death in industrialised countries. Many new molecular targets are being studied to improve atherosclerosis treatment and reduce the number of deaths. The action on these targets could lead to a decrease of blood cholesterol levels or produce a direct anti-atherosclerotic effect on the vascular wall. A cholesterol lowering effect could be achieved by reducing cholesterol synthesis (squalene synthase inhibitors), intestinal cholesterol absorption as well as intestinal and liver lipoprotein secretion (microsomal transfer protein inhibitors, acyl-coenzyme A-cholesterol acyltransferase inhibitors) or by increasing fecal excretion of bile acids (ileal sodium-dependent bile acid transporter inhibitors). An anti-atherosclerotic effect on the vascular wall could be achieved by reducing the inflammation via activation of peroxisome proliferator activated receptors, or, more particularly, could consist of decreased expression of adhesion molecules and chemoattractant proteins. Increasing the adenosine triphosphate-binding cassette A1 protein and inhibiting acyl-coenzyme A:cholesterol acyltransferase 1 activity could slow down formation of foam cells, which are a hallmark of atherosclerosis. Finally, the cholesterol fraction carried by high density lipoproteins, which is inversely correlated to cardiovascular risk, could be increased by cholesterol ester transfer protein inhibitors. All of these new classes of compounds are currently studied by pharmaceutical companies and are in different phases of development (preclinical or clinical). |
| Cholesterol metabolism, digestion rates and postprandial changes in serum of swine fed purified diets containing either casein or soybean protein Beynen, A. C., C. E. West, et al. (1990), J Nutr 120(5): 422-30. Abstract: Swine fitted with re-entrant ileo-cecal cannulas were fed purified diets containing either casein or soybean protein to study possible relations between cholesterol metabolism, digestion of dietary constituents and postprandial patterns of various serum components. Compared with soybean protein, dietary casein produced an increase in serum total cholesterol in which the excess cholesterol was located in the low density lipoprotein fraction. Ileal and fecal excretion of neutral steroids was diminished in pigs fed casein, suggesting that cholesterol absorption was stimulated. The apparent ileal absorption of protein was increased in pigs fed casein. The enhanced absorption of cholesterol and protein was associated with a reduced rate of flow of chyme through the ileum. The output of bile acids in the feces of pigs fed casein was decreased, whereas the ileal output was not significantly affected. This could be attributed to increased uptake of bile acids from the cecum and/or colon, which may in part be related to the indirectly observed decreased formation of secondary bile acids. Postprandial serum concentrations of insulin and glucose were temporarily increased in pigs fed casein, whereas those of triglycerides were decreased. We suggest that the decreased excretion of cholesterol and bile acids is the major determinant of casein-induced hypercholesterolemia in swine. |
| Cholesterol metabolsim defect associated with Conradi-Hunerman-Happle syndrome DiPreta, E. A., K. J. Smith, et al. (2000), Int J Dermatol 39(11): 846-50. Abstract: We present a 6-week-old black girl with Conradi-Hunerman-Happle syndrome (CHS). The mother had no past medical history of illness, and the pregnancy progressed normally to a spontaneous vaginal delivery at 36 weeks. There was no known significant family history. A diagnosis of chondrodysplasia punctata was made at birth from physical examination and X-ray findings. On physical examination at 6 weeks, a koala face, a saddle nose, and a right-sided cataract were noted (Fig. 1a,b). There was unilateral left-sided ichthyosis well demarcated at the midline, with whorled brown fine scale following Blashko's lines on the patient's right side. Orthopedic complications were bilateral but were more pronounced on the left side. There was bilateral shortening of the humerus, with polydactyly of the right hand, arachnodactyly of the left fingers, bilateral clubbing, and mild contractures of the feet. X-Rays showed multiple calcifications along the spine, proximal and distal femoral epiphysis, and proximal humeral epiphysis (Fig. 2). The patient was treated with emollients (aquaphor) twice daily with continuing improvement in ichthyosis. The clubbed feet were treated with splinting and the polydactyly was corrected by surgery. Ophthalmology was to follow the patient for her right-sided cataract. At the patient's 4-month follow-up, the ichthyosis showed a marked improvement with some residual hypo- pigmented atrophoderma noted. The distribution remained unchanged. Biopsies taken of ichthyotic lesions showed compact hyperkeratosis and follicular plugging. Vesicles within the stratum corneum contained amorphous material (Fig. 3a,b). The granular cell layer was thickened with retained oval nuclei. The epidermal and adnexal epithelium were disorganized. Increased apoptotic/dyskeratotic keratinocytes were seen within the epidermis, but were most evident within the follicular epithelium. Ultrastructural studies showed saccular dilations of the acellular space within the stratum corneum. These acellular spaces were filled with unprocessed lamellated pleated sheets and vesicle complexes and processed lamellae. Dyskeratotic cells were seen within the stratum spinosum. Red blood cell (RBC) plasmalogen levels and polyunsaturated fatty acids (PUFA), including decosahexaenoic acid (DHA), were within normal limits. Plasma very long chain fatty acids (VLCFA), including C26: 0/C22: 0 ratios, phytanic and pristanic acids, plasmalogen, and phytanic/pristanic ratios, trihydroxycholestanic acid (THCA) and dihydroxycholestanoic acid (DHCA) including their ratios, THCA/cholic acid and DHCA/chenodeoxycholic acid, and PUFAs including DHA were within normal limits. Urine organic acids and piecolic acid were within normal limits. Despite these normal values, there was an increase in cholest-8(9)-en-3beta-ol of 6.8 microg/mL (normal, 0.01-0.10 microg/mL) and an increase in 8-dehydrocholesterol (5.1 microg/mL) (normal, <0.10 microg/mL). |
| Cholesterol microcrystals associated with concanavalin A-binding glycoproteins contribute artifactually to nucleating activity assays Harvey, P. R., G. A. Upadhya, et al. (1995), J Lipid Res 36(12): 2661-9. Abstract: Concanavalin A (Con A) affinity chromatography is the standard procedure to separate cholesterol nucleating biliary proteins from lipids and pigment. We observed that even after extensive washing following application of bile, lipid contaminants remain. We have determined the contribution of lipid contamination to cholesterol nucleation and assessed a modified procedure to remove lipids from the column. Human gallbladder bile was spiked with 3Hcholesterol and 14Cphospholipid and applied to two sets of Con A-Sepharose columns. One column was washed in the usual manner with Tris-HCl buffer and the other with buffer containing 10 mM taurocholate prior to eluting bound glycoproteins with alpha-D-methylmannopyranoside. Eluted proteins were added to heated abnormal bile at a final concentration of 250 micrograms/ml to study the effect on cholesterol nucleation. A separate aliquot (20 microliter) of the protein solutions was counted for radioactivity. Cholesterol nucleating activity was less in samples from columns washed with 10 mM taurocholate than in samples from columns not washed with the bile salt. Lipid radioactivity was associated with Con A-binding proteins prepared without taurocholate, but not in those prepared with taurocholate wash. Light microscopy revealed the presence of cholesterol microcrystals and vesicles in some Con A-binding protein preparations prepared without a taurocholate wash. However, pellets from ultracentrifuged Con A preparations prepared without a bile salt wash revealed cholesterol crystals in all samples (n = 6). Washing with taurocholate did not affect recovery of protein mass and appearance of bands on SDS-PAGE gel showed an identical pattern in the two groups. This modified procedure to prepare potential nucleating proteins from gallbladder bile should eliminate erroneous results that may arise due to lipid contamination. |
| Cholesterol microemboli Ibsen, H. H., F. Brandrup, et al. (1992), Ugeskr Laeger 154(12): 774-6. Abstract: Cholesterol microemboli are caused by cholesterol crystals released from arteriosclerotic plaques in the major arteries. The clinical picture is illustrated by two case histories with symptoms in the form of myalgia, livedo reticularis and gangrene. The diagnoses were verified by demonstration of cholesterol crystals in the affected tissue. The pathogenesis is illustrated and, on the basis of the literature, it is emphasized that cholesterol microemboli are probably often overlooked clinically and that an increasing incidence must be anticipated on account of the increasing frequency of invasive procedures and treatments of arteriosclerotic vascular disease. |
| Cholesterol microembolization and stable renal function with continued anticoagulation Acker, C. G. (1992), South Med J 85(2): 210-2. Abstract: Cholesterol microembolization as a sequela of oral anticoagulant therapy has been reported to cause infarction of virtually any organ, often resulting in death. Until recently, discontinuance of anticoagulant therapy has been recommended, as this cessation has been shown to slow or halt further tissue infarction. I have described a patient with a prosthetic heart valve in whom the purple toes syndrome developed. Stable renal function followed the initiation of high-dose subcutaneous heparin therapy. |
| Cholesterol mobilization and regression of atheroma in cholesterol-fed rabbits induced by large unilamellar vesicles Rodrigueza, W. V., S. K. Klimuk, et al. (1998), Biochim Biophys Acta 1368(2): 306-20. Abstract: The antiatherogenic properties of repeated injections of egg phosphatidylcholine large unilamellar vesicles (LUVs) of 100 nm diameter were tested in an experimental model for atherosclerosis. Forty eight rabbits were divided into two diet groups fed standard rabbit chow or fed a cholesterol-enriched diet (0.5% by weight) to induce the formation of atherosclerotic lesions. Prior to the initiation of LUV therapy, the cholesterol diet was ceased and all animals were returned to standard rabbit chow. The treatment protocol consisted of a total of 10 bolus injections of vesicles, at a phospholipid dose of 300 mg/kg body weight or the equivalent volume of saline, with one injection given to each animal every 10 days. LUV injections brought about a large movement of cholesterol into the blood pool and resulted in a significant reduction in the cholesterol content as well as the degree of surface plaque involvement of aortic tissue in atherosclerotic animals. Most notably, the thoracic aorta of LUV-treated animals exhibited a 48% reduction in tissue cholesterol content per gram of protein compared to saline-treated controls. Histochemical analyses revealed that aortas from animals receiving the repeated injections of LUVs displayed less cholesterol deposits in lesions, and a moderate reduction in intimal-to-medial thickness. This regression of atheroma, induced by LUV therapy, was observed even though animals possessed persistent elevated plasma cholesterol levels after the cholesterol-enriched diet was ceased. These results suggest that repeated injections of LUVs, working with endogenous HDL, may be a useful therapy in the management of atherosclerosis. |
| Cholesterol mobilization by free and lipid-bound apoAI(Milano) and apoAI(Milano)-apoAII heterodimers Wang, W. Q., A. S. Moses, et al. (2001), Biochemistry 40(12): 3666-73. Abstract: Despite very low plasma levels of HDL, carriers of the apolipoprotein AI Arg173 --> Cys mutation apoAI(Milano) (AIM) have no apparent increase in risk for atherosclerotic vascular disease. HDL apolipoprotein species in AIM carriers include apoAI-AII heterodimers, previously found to confer the enhanced ability of tyrosyl radical-oxidized HDL to mobilize cholesterol for removal from cultured cells. To determine whether enhanced mobilization of cholesterol by apoprotein species in AIM explains a cardioprotective action of this mutation, we examined the ability of lipid-free and lipid-bound AIM and AIM-AII heterodimers to deplete cholesterol from cultured cells. Free AIM and AIM-AII heterodimers showed a decreased capacity to act as acceptors of cholesterol from cholesterol-loaded human fibroblasts compared with native apoAI but similar capacities to deplete fibroblasts of the pool of cholesterol available for esterification by acyl-CoA:cholesterol acyltransferase (ACAT). Discoidal reconstituted HDL (rHDL) containing apoAI depleted both of these cholesterol pools more readily than AIM-containing rHDL when compared at equivalent rHDL protein levels, but similar abilities of these rHDL to deplete cell cholesterol were seen when compared at equivalent phospholipid levels. Spherical rHDL generated using the whole lipid fraction of HDL and apoAI or AIM showed similar capacities to deplete total and ACAT-accessible cell cholesterol when compared at similar protein levels, but an increased capacity of AIM-containing particles was seen when compared at equivalent phospholipid levels. Unlike the apoAI-AII heterodimer in tyrosylated HDL, AIM-AII heterodimer-containing spherical rHDL showed no increased capacity to deplete either of these pools of cholesterol. These results suggest a similar or better capacity of native apoAI in lipid-free or lipid-bound form in discoidal rHDL to enhance the mobilization of cellular cholesterol when compared to AIM in its free or lipid-bound forms. Any increase in depletion of cellular cholesterol by lipid-bound AIM in spherical rHDL appears related to altered phospholipid-binding rather than intrinsic cholesterol-mobilizing characteristics of this protein compared to native apoAI. The lack of major differences in these studies in cholesterol mobilization by native apoAI and AIM, or by apoAIM-AII heterodimers, suggests that any protection against atherosclerosis conferred by this mutation is likely related to other beneficial vascular effects of AIM. |
| Cholesterol modification of Hedgehog family proteins Jeong, J. and A. P. McMahon (2002), J Clin Invest 110(5): 591-6. |
| Cholesterol modification of hedgehog is required for trafficking and movement, revealing an asymmetric cellular response to hedgehog Gallet, A., R. Rodriguez, et al. (2003), Dev Cell 4(2): 191-204. Abstract: Hedgehog family members are secreted proteins involved in numerous patterning mechanisms. Different posttranslational modifications have been shown to modulate Hedgehog biological activity. We investigated the role of these modifications in regulating subcellular localization of Hedgehog in the Drosophila embryonic epithelium. We demonstrate that cholesterol modification of Hedgehog is responsible for its assembly in large punctate structures and apical sorting through the activity of the sterol-sensing domain-containing Dispatched protein. We further show that movement of these specialized structures through the cellular field is contingent upon the activity of proteoglycans synthesized by the heparan sulfate polymerase Tout-Velu. Finally, we show that the Hedgehog large punctate structures are necessary only for a subset of Hedgehog target genes across the parasegmental boundary, suggesting that presentation of Hedgehog from different membrane compartments is responsible for Hedgehog functional diversity in epithelial cells. |
| Cholesterol modification of hedgehog signaling proteins in animal development Porter, J. A., K. E. Young, et al. (1996), Science 274(5285): 255-9. Abstract: Hedgehog (Hh) proteins comprise a family of secreted signaling molecules essential for patterning a variety of structures in animal embryogenesis. During biosynthesis, Hh undergoes an autocleavage reaction, mediated by its carboxyl-terminal domain, that produces a lipid-modified amino-terminal fragment responsible for all known Hh signaling activity. Here it is reported that cholesterol is the lipophilic moiety covalently attached to the amino-terminal signaling domain during autoprocessing and that the carboxyl-terminal domain acts as an intramolecular cholesterol transferase. This use of cholesterol to modify embryonic signaling proteins may account for some of the effects of perturbed cholesterol biosynthesis on animal development. |
| Cholesterol modification of proteins Mann, R. K. and P. A. Beachy (2000), Biochim Biophys Acta 1529(1-3): 188-202. Abstract: The demonstration over 30 years ago that inhibitors of cholesterol biosynthesis disrupt animal development suggested an intriguing connection between fundamental cellular metabolic processes and the more global processes of embryonic tissue patterning. Adding a new dimension to this relationship is the more recent finding that the Hedgehog family of tissue patterning factors are covalently modified by cholesterol. Here we review the mechanism of the Hedgehog autoprocessing reaction that results in this modification, and compare this reaction to that undergone by other autoprocessing proteins. We also discuss the biological consequences of cholesterol modification, in particular the use of cholesterol as a molecular handle in the spatial deployment of the protein signal in developing tissues. Finally, the developmental consequences of chemical and genetic disruption of cholesterol homeostasis are summarized, along with the potential importance of cholesterol-rich lipid rafts in production of and response to the Hh signal. |
| Cholesterol modification of sonic hedgehog is required for long-range signaling activity and effective modulation of signaling by Ptc1 Lewis, P. M., M. P. Dunn, et al. (2001), Cell 105(5): 599-612. Abstract: Sonic hedgehog (Shh) signaling from the posterior zone of polarizing activity (ZPA) is the primary determinant of anterior-posterior polarity in the vertebrate limb field. An active signal is produced by an autoprocessing reaction that covalently links cholesterol to the N-terminal signaling moiety (N-Shh(p)), tethering N-Shh(p) to the cell membrane. We have addressed the role played by this lipophilic modification in Shh-mediated patterning of mouse digits. Both the distribution and activity of N-Shh(p) indicate that N-Shh(p) acts directly over a few hundred microns. In contrast, N-Shh, a form that lacks cholesterol, retains similar biological activity to N-Shh(p), but signaling is posteriorly restricted. Thus, cholesterol modification is essential for the normal range of signaling. It also appears to be necessary for appropriate modulation of signaling by the Shh receptor, Ptc1. |
| Cholesterol modifies classical conditioning of the rabbit (Oryctolagus cuniculus) nictitating membrane response Schreurs, B. G., C. A. Smith-Bell, et al. (2003), Behav Neurosci 117(6): 1220-32. Abstract: Cholesterol plays an important role in synapse formation, receptor function, and synaptic plasticity, and animal studies show that modifying cholesterol may improve learning and memory. Other data show that feeding animals cholesterol can induce beta amyloid accumulation. Rabbits (Oryctolagus cuniculus) fed 2% cholesterol for 8 weeks were given trace conditioning of the nictitating membrane response using a 100-ms tone, a 700-ms trace, and periorbital electrical stimulation or airpuff. Rabbits fed cholesterol showed significant facilitation of trace conditioning to airpuff and conditioning-specific reflex modification to periorbital electrical stimulation and airpuff. The cholesterol-fed rabbits had beta amyloid accumulation in the cortex, but little in the hippocampus. The data suggest cholesterol had facilitative effects that outweighed potential amnesic effects of cortical beta amyloid. |
| Cholesterol modifies the gating of Kv1.3 in human T lymphocytes Hajdu, P., Z. Varga, et al. (2003), Pflugers Arch 445(6): 674-82. Abstract: The Kv1.3 potassium channel that belongs to the Shaker family of voltage-gated K(+) channels plays a crucial role in the mitogenic response of T cells. Because it spans the cell membrane its function can be influenced by lipid-protein interactions. In order to study the effect of lipid-protein interactions on the functioning of Kv1.3 we manipulated the membrane cholesterol content in T cells mimicking various physiological conditions by means of the oligosaccharide methyl-beta-cyclodextrin (MbetaCD) and its cholesterol-saturated complex (MbetaCD/C). Fluorescence polarization anisotropy and peak current density were used to monitor the efficiency of cholesterol removal (MbetaCD) and loading (MbetaCD/C). Using whole-cell patch-clamp technique we determined the kinetic and steady-state parameters of activation and inactivation of the Kv1.3 currents under different treatment conditions. Upon elevation of cholesterol content by 1 or 1.5 mg/ml MbetaCD/C the rates of both activation and inactivation were slowed. Moreover, the increased cholesterol level in the membrane resulted in a biphasic activation curve. Cholesterol depletion with MbetaCD (0.95 and 1.425 mg/ml) caused no significant changes in the gating characteristics of Kv1.3. The equilibrium between the open and the closed states of the channels was affected by increased cholesterol content, but at the same time steady-state inactivation was unchanged. We argue that manipulation of membrane cholesterol changed both the kinetic properties of Kv1.3 and steady-state parameters of activation by modifying lipid-protein interactions. |