Epsin binds to the EH domain of POB1 and regulates receptor-mediated endocytosis.
POB1 has been identified as a RalBP1-binding protein and has the Eps15 homology (EH) domain. The EH domain-containing proteins have been suggested to be involved in clathrin-dependent endocytosis. To clarify the function of POB1, we purified a protein which binds to the EH domain of POB1 from bovine brain cytosol and identified it as Epsin, which is known to bind to the EH domain of Eps15. Epsin has three Asn-Pro-Phe (NPF) motifs in the C-terminal region, which are known to form the core sequence for the binding to the EH domain. The EH domain of POB1 interacted directly with the region containing the NPF motifs of Epsin. Expression of Epsin in CHO-IR cells inhibited internalization of insulin although it affected neither insulin-binding nor autophosphorylation activities of the insulin receptor. Taken together with the observations that Epsin is involved in internalization of the receptors for epidermal growth factor and transferrin, these results suggest that Epsin is a binding partner of POB1 and their binding regulates receptor-mediated endocytosis.
Morinaka
K
K
Department of Biochemistry, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Koyama
S
S
Nakashima
S
S
Hinoi
T
T
Okawa
K
K
Iwamatsu
A
A
Kikuchi
A
A
D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D019556:COS Cells; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary; D004705:Endocytosis; D006801:Humans; D007328:Insulin / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins
D033942:Adaptor Proteins, Vesicular Transport; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D010750:Phosphoproteins; C489722:REPS2 protein, human; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins; C114154:epsin