van Dam Ellen M, Ten Broeke Toine, Jansen Karen, Spijkers Patricia, Stoorvogel Willem
Department of Cell Biology, University Medical Center and Institute of Biomembranes, Utrecht University, The Netherlands.
J Biol Chem. 2002 Dec 13;277(50):48876-83. doi: 10.1074/jbc.M206271200. Epub 2002 Oct 7.
Recycling of endocytosed membrane proteins involves passage through early endosomes and recycling endosomes. Previously, we demonstrated a role for clathrin-coated vesicles in transferrin receptor recycling. These clathrin-coated vesicles are formed from recycling endosomes in a process that was inhibited in dynamin-1(G273D)-overexpressing cells. Here we show a second transferrin recycling pathway, which requires phosphatidylinositol 3-kinase activity. Two unrelated phosphatidylinositol 3-kinase inhibitors, LY294002 and wortmannin, retained endocytosed transferrin in early endosomes but did not affect transfer through recycling endosomes. The inhibitory effects of LY294002 and dynamin-1(G273D) on transferrin recycling were additive. In combination with brefeldin A, a drug that prevents the formation of clathrin-coated buds at recycling endosomes, LY294002 inhibited transferrin recycling synergistically. Collectively, these data indicate two distinct recycling pathways. One pathway involves transfer from early endosomes to recycling endosomes, from where clathrin/dynamin-coated vesicles provide for further transport, whereas the other route bypasses recycling endosomes and requires phosphatidylinositol 3-kinase activity.
内吞的膜蛋白回收涉及通过早期内体和回收内体。此前，我们证明了网格蛋白包被囊泡在转铁蛋白受体回收中的作用。这些网格蛋白包被囊泡由回收内体形成，此过程在过表达发动蛋白-1（G273D）的细胞中受到抑制。在此我们展示了第二条转铁蛋白回收途径，该途径需要磷脂酰肌醇3激酶活性。两种不相关的磷脂酰肌醇3激酶抑制剂LY294002和渥曼青霉素，使内吞的转铁蛋白滞留在早期内体中，但不影响其通过回收内体的转运。LY294002和发动蛋白-1（G273D）对转铁蛋白回收的抑制作用具有累加性。与布雷菲德菌素A（一种阻止在回收内体形成网格蛋白包被芽的药物）联合使用时，LY294002协同抑制转铁蛋白回收。总体而言，这些数据表明存在两条不同的回收途径。一条途径涉及从早期内体转运至回收内体，网格蛋白/发动蛋白包被囊泡从回收内体提供进一步转运，而另一条途径绕过回收内体，且需要磷脂酰肌醇3激酶活性。
