Abstract
Endophilin 1 (Endo1) participates in synaptic vesicle biogenesis through interactions of its Src homology 3 domain with the polyphosphoinositide phosphatase Synaptojanin and the GTPase Dynamin. Endo1 has also been reported to affect endocytosis by converting membrane curvature via its lysophosphatidic acid acyltransferase activity. Here we report that a closely related isoform of Endo1, Endo3, inhibits clathrin-mediated endocytosis. Mutational analyses showed that the variable region of Endo3 is important in regulating transferrin endocytosis. In the brain, Endo3 is co-localized with dopamine D2 receptor in olfactory nerve terminals and inhibits its clathrin-mediated endocytosis in COS-7 cells. Furthermore, overexpression of Endo3 in an olfactory epithelium-derived cell line suppressed dopamine D2 receptor-mediated endocytosis and therefore accelerated its dopamine-induced differentiation. These results indicate that Endo3 may act as a negative regulator of clathrin-mediated endocytosis in brain neurons.
Highlights
Inhibition of Transferrin Endocytosis by Endophilin 3—To clarify the role of Endo3 in clathrin-mediated endocytosis, we assayed the effect of Endo3 on transferrin uptake [31] by transient expression of endo3 in COS-7 cells, with an empty vector or endo1 as controls
While overexpression of endo3 in COS-7 cells was associated with the arrest of transferrin endocytosis, this inhibition of transferrin uptake was abolished by replacing the variable region of Endo3 with that of Endophilin 1 (Endo1)
Endo3 inhibited the endocytosis of dopamine D2 receptors localized on olfactory nerve terminals, and this inhibition facilitated the dopamine-induced differentiation of a cell line derived from olfactory epithelium
Summary
Endo3 is co-localized with dopamine D2 receptor in olfactory nerve terminals and inhibits its clathrin-mediated endocytosis in COS-7 cells. Overexpression of Endo3 in an olfactory epithelium-derived cell line suppressed dopamine D2 receptor-mediated endocytosis and accelerated its dopamine-induced differentiation.
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