| Summary: | 碩士 === 國立臺灣大學 === 分子醫學研究所 === 93 === ADP-ribosylation factor like (ARL) proteins are one subfamily of ADP-ribosylation factor (ARF) small GTP binding protein family. Little is known about a human ARL protein, ARL5. Here we characterized the biologic properties and functions of hARL5 and described several novel observations. ARL5 expressed ubiquitously in many mammalian cell lines. In COS-7 cells, endogenous ARL5 and overexpressed GFP-ARL5 localized to centrosomes through out the cell cycle with exception of midbody localization during cytokinesis. By yeast two-hybrid screening, a microtubule plus-end binding protein EB1 was identified as an interacting partner of ARL5. ARL5 also interacted with EB1 in vivo. To investigate the biologic functions of ARL5, RNAi knockdown was performed. In ARL5 knockdown COS-7 cells, the microtubule regrowth from and anchoring at centrosomes were delayed and disordered similar to the defects caused by EB1 knockdown. Furthermore, overexpressed wild type and constitutively active form (ARL5Q80L) of ARL5 were diffused and partially localized to endosomes in COS-7 cells. The heterogeneous distributions of ARL5 constitutively inactive form (ARL5T35N) at endosomes, mitochondria, and aggresome-like compartments provided a distinct feature of ARL5. In addition, ARL5T35N diminished mitochondria membrane potential through its C-terminal region when it localized to mitochondria. Taken together, we infer that ARL5 might regulate different cellular processes, including centrosome-mediated microtubule nucleation and anchoring, vesicle trafficking, mitochondrial function, and protein degradation.
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