Sterol carrier protein-2 expression alters phospholipid content and fatty acyl composition in L-cell fibroblasts.
The effects sterol carrier protein-2 (SCP-2) expression on L-cell phospholipid levels and fatty acyl composition was assessed using L-cells transfected with the murine cDNA encoding for either the 15 kDa proSCP-2 or 13.2 kDa SCP-2. Expression of these proteins reduced total phospholipid mass (nmol/mg protein) by 24% and reduced the cholesterol to phospholipid ratio 60 and 28%, respectively. In 15 kDa proSCP-2 expressing cells, individual phospholipid class masses, excluding sphingomyelin (CerPCho), were reduced as follows: phosphatidylinositol (PtdIns) and phosphatidylserine (PtdSer) >> ethanolamine glycerophospholipid (EtnGpl) > choline glycerophospholipid (ChoGpl). Furthermore, ethanolamine plasmalogen mass was decreased 25%, while choline plasmalogen mass was elevated 30% in 15 kDa proSCP-2 expressing cells. In 13.2 kDa SCP-2 expressing cells, phospholipid class mass was decreased as follows: PtdIns and PtdSer >> ChoGpl. These changes in phospholipid mass resulted in altered cellular phospholipid composition. Expression of either protein differentially altered the type of fatty acid esterified onto the phospholipids. These effects included a greater proportion of polyunsaturated fatty acids and a reduction in saturated fatty acids, although 15 kDa proSCP-2 expression had a more robust effect on these parameters than did 13.2 kDa SCP-2 expression. In summary, expression of SCP-2 reduced individual phospholipid class mass, except for CerPCho, and altered the fatty acid composition of each phospholipid class examined. These results clearly demonstrate that SCP-2 expression altered basal phospholipid levels, suggesting that SCP-2 can alter the function of endoplasmic reticulum phospholipid synthetic enzymes.
Murphy
E J
EJ
Department of Pharmacology and Physiology, Texas A&M University, TVMC, College Station, TX 77843-4466, USA.
Stiles
T
T
Schroeder
F
F
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D002784:Cholesterol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D015870:Gene Expression; D007739:L Cells; D051379:Mice; D020675:Peroxisomes / Q000378:metabolism; D010743:Phospholipids / Q000145:classification / Q000378:metabolism*; D010940:Plant Proteins; D010955:Plasmalogens / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics; D013261:Sterols / Q000378:metabolism*; D014162:Transfection
D002352:Carrier Proteins; D005227:Fatty Acids; D010743:Phospholipids; D010940:Plant Proteins; D010955:Plasmalogens; D011498:Protein Precursors; D013261:Sterols; C072087:sterol carrier proteins; D002784:Cholesterol