CELL BIOLOGICAL RESEARCH WITH THE MOLECULAR MECHANISMS OF LIPID DROPLETS FORMATION AND LIPID METABOLISM, TRANSFORMATION.

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TYROSINE PHSPHORYLATION OF CAVEOLIN-1 IN THE ENDOTHELIUM.1) Tyrosine phosphorylation of caveolin-1 occurred in limited locations, including the endothelium of the continuous capillaries and small venules. 2) Cultured endothelial cells were not labeled by PY14 under a standard culture condition, but became positively labeled when exposed to oxidative stresses and/or tyrosine phosphatase inhibitors. 3) The reaction was prohibited by pretreating with herbimycin A or genistein. Vasoactive reagents or physical stimuli did not cause the phosphorylation. 4) The number of invaginated caveolae decreased drastically, and vesicles labeled intensely for caveolin-1 appeared in the cytoplasm ; the average diameter of the vesicles was larger than that of caveolae. 5) The results implies that tyrosine phosphorylation of caveolin-1 occurred at tyrosine-14 in the normal rat endothelium in vivo and may induce caveolar vesiculation and/or fusion.VIMEMTIN-RELATED ANTIGEN AROUND LIPID DROPLETE1) By using a … More monoclonal antibody (mAb A2) raised against the cytoskeleton of goldfish xanthophores, we found that a 190-kDa protein is localized along the rim of lipid droplets in rat pulmonary septal cells. 2) MAb A2 bound to the rim of lipid droplets in the septal cell in vivo. The circular labeling around lipid droplets as well as filamentous labeling in the cytoplasm was observed in cultured septal cells. 3) As the number and size of lipid droplets decreased in cells cultured for several days, the circular labeling became indistinct, whereas the filamentous labeling persisted. 4) In Western blotting, mAb A2 recognized 190-kDa and 58-kDa bands in the cultured septal cell, but the latter turned out to be vimentin. 5) Treatment of septal cells for 4 hr with Colcemid extinguished the labeling around the lipid droplets, and only labeling in a coarse bundle pattern that matched the anti-vimentin labeling pattern remained. 6) After more than 12 hr of Colcemid treatment, the circular labeling reappeared around the lipid droplets. The disappearance of the circular labeling also occurred when septal cells were treated with Taxol or cytochalasin B for more than 4 hr. Less