Localization of the pre-squalene segment of the isoprenoid biosynthetic pathway in mammalian peroxisomes.
Previous studies have indicated that the early steps in the isoprenoid/cholesterol biosynthetic pathway occur in peroxisomes. However, the role of peroxisomes in cholesterol biosynthesis has recently been questioned in several reports concluding that three of the peroxisomal cholesterol biosynthetic enzymes, namely mevalonate kinase, phosphomevalonate kinase, and mevalonate diphosphate decarboxylase, do not localize to peroxisomes in human cells even though they contain consensus peroxisomal targeting signals. We re-investigated the subcellular localization of the cholesterol biosynthetic enzymes of the pre-squalene segment in human cells by using new stable isotopic techniques and data computations with isotopomer spectral analysis, in combination with immunofluorescence and cell permeabilization techniques. Our present findings clearly show and confirm previous studies that the pre-squalene segment of the cholesterol biosynthetic pathway is localized to peroxisomes. In addition, our data are consistent with the hypothesis that acetyl-CoA derived from peroxisomal beta-oxidation of very long-chain fatty acids and medium-chain dicarboxylic acids is preferentially channeled to cholesterol synthesis inside the peroxisomes without mixing with the cytosolic acetyl-CoA pool.
Kovacs
Werner J
WJ
Department of Biology, San Diego State University, San Diego, CA, USA. werner.kovacs@anatomie.med.uni-giessen.de
Tape
Khanichi N
KN
Shackelford
Janis E
JE
Duan
Xueying
X
Kasumov
Takhar
T
Kelleher
Joanne K
JK
Brunengraber
Henri
H
Krisans
Skaidrite K
SK
D000101:Acetyl-CoA C-Acetyltransferase / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D019748:Carbon-Carbon Double Bond Isomerases / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000187:drug effects; D002784:Cholesterol / Q000096:biosynthesis; D006224:Cricetinae; D003412:Cricetulus; D004072:Digitonin / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D051228:Geranyltranstransferase / Q000378:metabolism; D045782:Hemiterpenes; D006801:Humans; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000378:metabolism; D007150:Immunohistochemistry; D007202:Indicators and Reagents / Q000494:pharmacology; D008113:Liver Neoplasms / Q000473:pathology; D020675:Peroxisomes / Q000201:enzymology / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000378:metabolism; D013185:Squalene / Q000378:metabolism*; D013729:Terpenes / Q000378:metabolism*
D005227:Fatty Acids; D045782:Hemiterpenes; D007202:Indicators and Reagents; D013729:Terpenes; D013185:Squalene; D002784:Cholesterol; D000101:Acetyl-CoA C-Acetyltransferase; D006904:Hydroxymethylglutaryl-CoA Synthase; D051228:Geranyltranstransferase; D017853:Phosphotransferases (Alcohol Group Acceptor); C021796:mevalonate kinase; D017856:Phosphotransferases (Phosphate Group Acceptor); C022371:phosphomevalonate kinase; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase; C007547:behenic acid; D004072:Digitonin