Characterization of myotubularin-related protein 7 and its binding partner, myotubularin-related protein 9

被引:83
作者
Mochizuki, Y [1 ]
Majerus, PW [1 ]
机构
[1] Washington Univ, Sch Med, Dept Internal Med, St Louis, MO 63110 USA
关键词
D O I
10.1073/pnas.1333958100
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Myotubularin-related protein 7 (MTMR7) is a member of the myotubularin (MTM) family. The cDNA encoding the mouse MTMR7 contains 1,983 bp, and the predicted protein has a deduced molecular mass of 75.6 kDa. Northern and Western blot analyses showed that MTMR7 is expressed mainly in brain and mouse neuroblastoma N1E-115 cells. Recombinant MTMR7 dephosphorylated the D-3 position of phosphaticlylinositol 3-phosphate and inositol 1,3-bisphosphate [lns(1,3)P-2]. The substrate specificity of MTMR7 is different than other MTM proteins in that this enzyme prefers the water-soluble substrate. Immunofluorescence showed that MTMR7 is localized in Golgi-like granules and cytosol, and subcellular fractionation showed both cytoplasmic and membrane localization of MTMR7 in N1E-115 cells. An MTMR7-binding protein was found in an anti-MTMR7 immunciprecipitate from N1-115 cells and identified as MTM-related protein 9 (MTMR9) by tandem mass spectrometry. The coiled-coil domain of MTMR9 was sufficient for binding to MTMR7. The binding of MTMR9 increased the lns(1,3)P-2 phosphatase activity of MTMR7. Our results show that MTMR7 forms a complex with MTMR9 and dephosphorylates phosphatidylinositol 3-phosphate and lns(1,3)P-2 in neuronal cells.
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页码:9768 / 9773
页数:6
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