GLYCOSYLATION, DIMERIZATION, AND HEPARIN AFFINITY OF LIPOPROTEIN-LIPASE IN 3T3-L1 ADIPOCYTES

The relationship between glycosylation, dimerization, and heparin affi nity of lipoprotein lipase (LPL) was studied in 3T3-L1 adipocytes. Thr ee forms of LPL subunits were found in normal cells; totally endo H-re sistant (57 kDa), partially sensitive (54 kDa), and totally sensitive (51 kDa) forms. LPL in normal cells was active, dimeric, and showed hi gh affinity for heparin. LPL in cells treated with tunicamycin, preven ting the transfer of N-linked oligosaccharide chain, was unglycosylate d (51 kDa) and inactive. LPL proteins were found as an aggregate, and had low affinity for heparin. After treatment with castanospermine, an inhibitor of ER glucosidase I, 80% of LPL activity was inhibited. Mos t of LPL proteins were totally endo H-sensitive, present as an aggrega te, and had low affinity for heparin. LPL in cells treated with deoxym annojirimycin, an inhibitor of Golgi mannosidase I, was active, dimeri c, and had high affinity for heparin as in normal cells. But LPL subun its were all endo H-sensitive. These results suggest that core glycosy lation and subsequent removal of glucose residue is required, but proc essing after Golgi mannosidase I is not necessary for dimerization and acquisition of high heparin affinity of LPL.