Sac domain-containing proteins belong to a newly identified family of phosphoinositide phosphatases （the PIPPase family）. Despite well-characterized enzymatic activity, the biological functions of this mammalian Sac...Sac domain-containing proteins belong to a newly identified family of phosphoinositide phosphatases （the PIPPase family）. Despite well-characterized enzymatic activity, the biological functions of this mammalian Sac domain PIPPase family remain largely unknown. We identified a novel Sac domain-containing protein, rat Sac3 （rSac3）, which is widely expressed in various tissues and localized to the endoplasmic reticulum, Golgi complex and recycling endosomes, rSac3 displays PIPPase activity with PI（3）P, PI（4）P and PI（3,5）P2 as substrates in vitro, and a mutation in the catalytic core of the Sac domain abolishes its enzymatic activity. The expression of rSac3 is upregulated during nerve growth factor （NGF）-stimulated PC 12 cell neuronal differentiation, and overexpression of this protein promotes neurite outgrowth in PC 12 cells. Conversely, inhibition ofrSac3 expression by antisense oligonucleotides reduces neurite outgrowth of NGF- stimulated PC 12 cells, and the active site mutation of rSac3 eliminates its neurite-outgrowth-promoting activity. These results indicate that rSac3 promotes neurite outgrowth in differentiating neurons through its PIPPase activity, suggesting that Sac domain PIPPase proteins may participate in forward membrane trafficking from the endoplasmic reticulum and Golgi complex to the plasma membrane, and may function as regulators of this crucial process of neuronal cell growth and differentiation.展开更多
基金We thank Dr Bin Zhang （University of Michigan, USA） for providing the MCFD2 antibodies. This work was supported in part by the Life Science Special Fund of the Chinese Academy of Sciences for Human Genome Research （KJ95T-06 and KSCX1-Y02 to BML, NHJ and MLJ）, the National Natural Science Foundation of China （30225023 and 30430240 to BML and 90208011, 30300174, 30470856, 30421005 and 30623003 to NHJ）, the National Key Basic Research and Development Program of China （2006CB500807 to BML and 2002CB713802, 2005CB522704 and 2006CB943902 to NHJ）, the National High-Tech Research and Development Program of China （2006AA02ZI99 to BML and 2006AA02Z186 to NHJ）, the Shanghai Key Project of Basic Science Research （04DZ14005 to BML and 04DZ14005, 04DZ05608, 06DJI4001 and 06DZ22032 to NHJ）, the Council of the Shanghai Municipal for Science and Technology （05814578 to NHJ）, and the US National Institutes of Health （DA013471 and DA020555 to LY）.
文摘Sac domain-containing proteins belong to a newly identified family of phosphoinositide phosphatases （the PIPPase family）. Despite well-characterized enzymatic activity, the biological functions of this mammalian Sac domain PIPPase family remain largely unknown. We identified a novel Sac domain-containing protein, rat Sac3 （rSac3）, which is widely expressed in various tissues and localized to the endoplasmic reticulum, Golgi complex and recycling endosomes, rSac3 displays PIPPase activity with PI（3）P, PI（4）P and PI（3,5）P2 as substrates in vitro, and a mutation in the catalytic core of the Sac domain abolishes its enzymatic activity. The expression of rSac3 is upregulated during nerve growth factor （NGF）-stimulated PC 12 cell neuronal differentiation, and overexpression of this protein promotes neurite outgrowth in PC 12 cells. Conversely, inhibition ofrSac3 expression by antisense oligonucleotides reduces neurite outgrowth of NGF- stimulated PC 12 cells, and the active site mutation of rSac3 eliminates its neurite-outgrowth-promoting activity. These results indicate that rSac3 promotes neurite outgrowth in differentiating neurons through its PIPPase activity, suggesting that Sac domain PIPPase proteins may participate in forward membrane trafficking from the endoplasmic reticulum and Golgi complex to the plasma membrane, and may function as regulators of this crucial process of neuronal cell growth and differentiation.
