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Islet cell autoantigen of 69kDa (ICA69) is a small GTPase-binding protein of unknown function. ICA69 is enriched in the Golgi complex and its N-terminal half contains a BAR domain, a module that can bind/bend membranes and interacts with phospholipids. Here we show that in insulinoma INS-1 cells ICA69 binds to the small GTPase Rab2, which regulates the transport of COPI vesicles between the endoplasmic reticulum and the Golgi complex. Rab2 binds to ICA69 in a GTP-dependent fashion and recruits it to membranes. Over-expression of either Rab2 or ICA69 in INS-1 cells results in a phenotype characterized by: (i) impaired anterograde transport of the secretory granule protein precursors pro-ICA512 and chromogranin A; (ii) reduction of stimulated insulin secretion. Taken together, these data identify ICA69 as a novel Rab2 effector and point to its role in regulating the early transport of insulin secretory granule proteins.

Original publication

DOI

10.1016/j.ejcb.2007.11.003

Type

Journal article

Journal

Eur J Cell Biol

Publication Date

04/2008

Volume

87

Pages

197 - 209

Keywords

Autoantigens, Binding Sites, Cell Line, Tumor, Chromogranin A, Coatomer Protein, Endoplasmic Reticulum, Golgi Apparatus, Humans, Insulin, Insulinoma, Pancreatic Neoplasms, Protein Binding, Protein Transport, Receptor-Like Protein Tyrosine Phosphatases, Class 8, Secretory Vesicles, rab2 GTP-Binding Protein