Evidence for a novel keratinocyte fatty acid uptake mechanism with preference for linoleic acid: comparison of oleic and linoleic acid uptake by cultured human keratinocytes, fibroblasts and a human hepatoma cell line.
Keratinocytes require the essential fatty acid (FA), linoleic acid (LA), for the synthesis of stratum corneum membrane lipids. A plasma membrane-FA binding protein (PM-FABP), is postulated to mediate cellular FA-uptake in hepatocytes and several other tissues, but the mechanism whereby exogenous FA are taken up by keratinocytes has not been investigated. This study examines the uptake of LA and oleic acid (non-essential) in cultured human keratinocytes, in comparison to dermal fibroblasts and the human hepatoma cell line, HepG2. As previously reported for hepatocytes, FA-uptake in keratinocytes was curvilinear, with an initial (30 s) rapid cellular influx. The initial uptake component was temperature dependent, exhibited saturable kinetics and was significantly inhibited by pretreatment with trypsin. In contrast, fibroblast FA-uptake lacked an initial rapid uptake component, was relatively temperature insensitive, and was not inhibited by trypsin. Keratinocytes differed from both hepatocytes and fibroblasts by more rapid uptake of LA in comparison to oleic acid during the initial influx phase. Moreover, FA-uptake in keratinocytes was not inhibited by preincubation with a anti-rat liver PM-FABP antibody. These data provide evidence for a PM-FA transporter in keratinocytes that is distinct from the hepatic PM-FABP. The apparent preference of the putative keratinocyte FA transporter for LA may function to ensure epidermal capture of sufficient LA for barrier lipid synthesis.
Schürer
N Y
NY
Hautklinik, Heinrich Heine Universität Düsseldorf, Germany.
Stremmel
W
W
Grundmann
J U
JU
Schliep
V
V
Kleinert
H
H
Bass
N M
NM
Williams
M L
ML
D000328:Adult; D000906:Antibodies / Q000276:immunology; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D013696:Temperature; D014357:Trypsin; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D000906:Antibodies; D002352:Carrier Proteins; C107608:FABP7 protein, human; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D008041:Linoleic Acids; D008055:Lipids; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D025521:Tumor Suppressor Proteins; D019301:Oleic Acid; D019787:Linoleic Acid; D014357:Trypsin