Noc2, a putative zinc finger protein involved in exocytosis in endocrine cells.
We have cloned a cDNA encoding a novel protein of 302 amino acids (designated Noc2, no C2 domain) that has 40.7% amino acid identity with and 77.9% similarity to the N-terminal region of rabphilin-3A, a target molecule of Rab3A. However, unlike rabphilin-3A, Noc2 lacks two C2 domains that are thought to interact with Ca2+ and phospholipids. Noc2 is expressed predominantly in endocrine tissues and hormone-secreting cell lines and at very low levels in brain. Immunoblot analysis of subcellular fractions of the insulin-secreting cell line MIN6 and immunocytochemistry reveal that Noc2 is a 38-kDa protein present in the cytoplasm. Overexpression of Noc2 in PC12 cells cotransfected with growth hormone enhances high K+-induced growth hormone secretion. Screening a mouse embryonic cDNA library with the yeast two-hybrid system shows that Noc2 interacts with the LIM domain-containing protein zyxin, a component of the cytoskeleton, and this interaction is further confirmed by the coimmunoprecipitation experiment. Accordingly, Noc2 is probably involved in regulated exocytosis in endocrine cells by interacting with the cytoskeleton.
Kotake
K
K
Division of Molecular Medicine, Center of Biomedical Science, Chiba University School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260, Japan.
Ozaki
N
N
Mizuta
M
M
Sekiya
S
S
Inagaki
N
N
Seino
S
S
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D004702:Endocrine Glands / Q000378:metabolism*; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000737:chemistry; D047908:Intracellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000378:metabolism; D008667:Metalloproteins / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D016716:PC12 Cells; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D016335:Zinc Fingers; D060589:Zyxin; D020692:rab3 GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D008667:Metalloproteins; D011506:Proteins; C484660:Rph3al protein, mouse; C109307:Rph3al protein, rat; C498285:Zyx protein, mouse; D060589:Zyxin; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins