Sterol carrier protein-2 localization in endoplasmic reticulum and role in phospholipid formation.
Although sterol carrier protein-2 (SCP-2; also called nonspecific lipid transfer protein) binds fatty acids and fatty acyl-CoAs, its role in fatty acid metabolism is not fully understood. L-cell fibroblasts stably expressing SCP-2 were used to resolve the relationship between SCP-2 intracellular location and fatty acid transacylation in the endoplasmic reticulum. Indirect immunofluorescence double labeling and laser scanning confocal microscopy detected SCP-2 in peroxisomes > endoplasmic reticulum > mitochondria > lysosomes. SCP-2 enhanced incorporation of exogenous [(3)H]oleic acid into phospholipids and triacylglycerols of overexpressing cells 1.6- and 2.5-fold, respectively, stimulated microsomal incorporation of [1-(14)C]oleoyl-CoA into phosphatidic acid in vitro 13-fold, and exhibited higher specificity for unsaturated versus saturated fatty acyl-CoA. SCP-2 enhanced the rate-limiting step in microsomal phosphatidic acid biosynthesis mediated by glycerol-3-phosphate acyltransferase. SCP-2 also enhanced microsomal acyl-chain remodeling of phosphatidylethanolamine up to fivefold and phosphatidylserine twofold, depending on the specific fatty acyl-CoA, but had no effect on other phospholipid classes. In summary, these results were consistent with a role for SCP-2 in phospholipid synthesis in the endoplasmic reticulum.
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Department of Pathobiology, Texas A&M University, College Station, Texas 77843-4466, USA.
Jolly
C A
CA
Atshaves
B P
BP
Roths
J B
JB
Murphy
E J
EJ
Kier
A B
AB
Schroeder
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F
D000214:Acyl Coenzyme A / Q000378:metabolism; D000215:Acylation / Q000187:drug effects; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000378:metabolism; D007150:Immunohistochemistry; D007424:Intracellular Fluid / Q000378:metabolism; D007739:L Cells; D051379:Mice; D008856:Microscopy, Fluorescence; D008861:Microsomes / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D010712:Phosphatidic Acids / Q000096:biosynthesis; D010743:Phospholipids / Q000096:biosynthesis*; D010940:Plant Proteins; D011817:Rabbits; D013379:Substrate Specificity; D014162:Transfection; D014280:Triglycerides / Q000096:biosynthesis
D000214:Acyl Coenzyme A; D002352:Carrier Proteins; D005227:Fatty Acids; D010712:Phosphatidic Acids; D010743:Phospholipids; D010940:Plant Proteins; D014280:Triglycerides; C072087:sterol carrier proteins; D005992:Glycerol-3-Phosphate O-Acyltransferase