Fatty acylation of heparan sulfate proteoglycan from human colon carcinoma cells.
A number of transmembrane proteins have been recently reported to be modified by the covalent addition of saturated fatty acids which may contribute to membrane targeting and specific protein-lipid interactions. Such modifications have not been reported in cell-associated heparan sulfate proteoglycans, although these macromolecules are known to be hydrophobic. Here, we report that a cell surface heparan sulfate proteoglycan is acylated with both myristate and palmitate, two long-chain saturated fatty acids. When colon carcinoma cells were labeled with [3H]myristic acid, a significant proportion of the label was shown to be specifically incorporated into the protein core of the proteoglycan. Characterization of fatty acyl moiety in the purified proteoglycan by reverse-phase high pressure liquid chromatography revealed that approximately 60% of the covalently bound fatty acids was myristate. We further show that this relatively rare 14-carbon fatty acid was bound to the protein core via a hydroxylamine- and alkali-resistant amide bond. The remaining 40% was the more common 16-carbon palmitate, which was bound via a hydroxylamine- and alkali-sensitive thioester bond. Palmitate appeared to be added post-translationally and derived in part from intracellular elongation of myristate, a process that occurred within the first two hours and was insensitive to inhibition of protein synthesis. Acylation of heparan sulfate proteoglycan represents a novel modification of this gene product and could play a role in a number of biological functions including specific interactions with membrane receptors and ligand stabilization.
Iozzo
R V
RV
Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Kovalszky
I
I
Hacobian
N
N
Schick
P K
PK
Ellingson
J S
JS
Dodge
G R
GR
D000215:Acylation; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005227:Fatty Acids / Q000378:metabolism*; D006493:Heparin / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D006878:Hydroxides; D008055:Lipids / Q000302:isolation & purification; D000432:Methanol; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D011188:Potassium; D017680:Potassium Compounds; D011499:Protein Processing, Post-Translational; D011509:Proteoglycans / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D005227:Fatty Acids; D006878:Hydroxides; D008055:Lipids; D009227:Myristic Acids; D010169:Palmitic Acids; D017680:Potassium Compounds; D011509:Proteoglycans; C036090:heparin proteoglycan; D019814:Myristic Acid; D019308:Palmitic Acid; D006493:Heparin; D003513:Cycloheximide; D011188:Potassium; C029943:potassium hydroxide; D000432:Methanol