| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Golgins are a family of coiled-coil proteins associated with the Golgi apparatus necessary for tethering events in membrane fusion and as structural supports for Golgi cisternae. One of the golgin, giantin is an integral membrane protein anchored to the membrane by the COOH-terminal hydrophobic domain, and may be involved in the tethering process of the vesicular transport.
GCP60, which is peripherally associated with the Golgi membrane, was isolated as the giantin binding protein. In this report, we examined the region for Golgi targeting and retention of GCP60, and identified two distinct signals for correct localization of the protein. Structure analysis reveals functional domains and motifs in GCP60 amino acid sequence, those are proline rich domain (Pro-rich), acyl-CoA binding domain (ACBP), nuclear localizing signal (NLS) and Golgi dynamics domain (GOLD). The GOLD domain was identified as a novel β-strand-rich domain, in the p24 cargo receptor family of proteins, and several other proteins with roles in Golgi dynamics and secretion. It has been shown that overexpression of a region of GCP60 encompassing the GOLD domain caused disassembly of the Golgi structure and abrogated protein transport from the ER to the Golgi. Therefore, we explored the region for Golgi targeting and retention of GCP60, and identified two distinct signals for correct localization of the protein. Using the series of deletion mutants, it revealed that the Golgi targeting and retention of GCP60 is required both N- and C-terminal segments. In C-terminal segment, the GOLD domain is essential for the Golgi targeting and retention, especially two conserved tyrosine residues are required for giantin binding. On the contrary, the two phenylalanine residues in the N-terminal segment are involved in the ER export of GCP60. These results suggest that the GCP60 cycles between the ER-Golgi as Golgi resident membrane proteins.
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