Variation of liver-type fatty acid binding protein content in the human hepatoma cell line HepG2 by peroxisome proliferators and antisense RNA affects the rate of fatty acid uptake

The liver-type fatty acid binding protein (L-FABP), a member of a family of mostly cytosolic 14-15 kDa proteins known to bind fatty acids in vitro and in vivo, is discussed to play a role in fatty acid uptake. Cells of the he patoma HepG2 cell line endogenously express this protein to approximately 0 .2% of cytosolic proteins and served as a model to study the effect of L-FA BP on fatty acid uptake, by manipulating L-FABP expression in two approache s. First, L-FABP content was more than doubled upon treating the cells with the potent peroxisome proliferators bezafibrate and Wy14,643 and incubatio n of these cells with [1-C-14]oleic acid led to an increase in fatty acid u ptake rate from 0.55 to 0.74 and 0.98 nmol/min per mg protein, respectively . In the second approach L-FABP expression was reduced by stable transfecti on with antisense L-FABP mRNA yielding seven clones with L-FABP contents ra nging from 0.03% to 0.14% of cytosolic proteins. This reduction to one sixt h of normal L-FABP content reduced the rate of [1-C-14]oleic acid uptake fr om 0.55 to 0.19 nmol/min per mg protein, i.e., by 66%, The analysis of pero xisome proliferator-treated cells and L-FABP tnRNA antisense clones reveale d a direct correlation between L-FABP content and fatty acid uptake. (C) 19 99 Elsevier Science B.V. All rights reserved.