EXPRESSION AND REGULATION OF MESSENGER-RNA FOR PUTATIVE FATTY-ACID TRANSPORT RELATED PROTEINS AND FATTY ACYL COA SYNTHASE IN MURINE EPIDERMIS AND CULTURED HUMAN KERATINOCYTES

The epidermis has a requirement for fatty acids in order to synthesize cellular membranes and the extracellular lipid lamellar membranes in the stratum corneum, Despite high endogenous production of fatty acids the transport of exogenous essential fatty acids into the epidermis i s an absolute requirement. Fatty acid uptake by keratinocytes has been shown to be mediated by a transport system. In this study we determin ed in murine epidermis and human cultured keratinocytes the expression of three putative fatty acid transport related proteins and fatty acy l CoA synthase, an enzyme that facilitates the uptake of fatty acids b y promoting their metabolism. In cultured human keratinocytes, mRNA fo r fatty acid transport protein (FATP), plasma membrane fatty acid bind ing protein (FABP-pm), and fatty acyl CoA synthase (FACS) were detecta ble. Differentiation, induced by high calcium, did not affect FATP mRN A levels, but resulted in an approximate to 50% increase in FACS mRNA, while decreasing FABP-pm mRNA by 50%. Fatty acid translocase (FAT) mR NA was ndt detected in cultured human keratinocytes, In murine epiderm is, FATP, FABP-pm, FACS, and FAT mRNA were all present. Barrier disrup tion by either tape stripping or acetone treatment increased FAT mRNA levels by approximate to 2-fold without affecting FATP, FABP-pm, or FA CS. Occlusion with an impermeable membrane immediately after barrier d isruption completely blocked the increase in FAT mRNA levels, indicati ng that this increase is related to barrier disruption rather than a n onspecific injury effect. In summary, this study demonstrates that sev eral putative fatty acid transport related proteins as well as fatty a cyl CoA synthase are expressed in keratinocytes and epidermis, and tha t the expression of these proteins may be regulated by differentiation and/or barrier disruption.