作者: Michael J Schell , Michele Maurice , Bruno Stieger , Ann L Hubbard
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摘要: In hepatocytes, all newly synthesized plasma membrane (PM) proteins so far studied arrive first at the basolateral domain; apically destined are subsequently endocytosed and sorted to apical domain via transcytosis. A mechanism for sorting of glycophosphatidylinositol (GPI)-linked has been proposed whereby they associate in lipid microdomains trans-Golgi network then directly. Such a poses potential exception hepatocyte rule. We have used pulse-chase techniques conjunction with subcellular fractionation compare trafficking 5' nucleotidase (5NT), an endogenous GPI-anchored protein two transmembrane proteins. Using one-step technique separate highly enriched fraction Golgi-derived membranes from ER PM, we find that both 5NT polymeric IgA receptor (pIgAR) traverse Golgi apparatus high efficiency. method resolves PM vesicles derived domains, appears as early 30 min chase. However subsequent redistribution requires > 3.5 h chase reach steady state. This rate transcytosis is much slower than observed dipeptidylpeptidase IV, anchored single domain. propose slow related fact GPI-linked excluded clathrin-coated pits/vesicles, instead must be nonclathrin pathway.