MICELLAR LIPOPROTEINS AS THE POSSIBLE STORAGE AND TRANSLOCATION FORM OF INTRACELLULAR DIACYLGLYCEROL

Previous work indicated that diacylglycerol (DG) molecules translocate across the cytoplasm of mammalian cells, a process relevant to the si gnalling role of this lipid as protein kinase C activator. Here we inv estigated the possible mechanism underlying DG translocation. We exami ned the interaction between 1,2-di-[1-C-14]oleoyl-sn-glycerol and rat liver cytosol (rlc) using assays based on Lipidex-1000 and on coelutio n on Sepharose CL 6B, We measured high DG binding activity and found t hat it resides in cytosolic proteins and not in cytosolic lipids. Chro matography of rlc proteins on Sepharose CL 6B showed profiles in which the activity measured by either method coincided. Further, we showed that the DG-rlc protein interaction results in the stabilization of DG in a micellar form, eluting in the void volume of Sepharose CL 6B. Su ch stabilized micelles are reminiscent of insect lipophorins and may r epresent a new, thus far unrecognized, mode of lipid transport within living cells, (C) 1998 Academic Press.