Phosphoinositides (PIs) play important roles in the regulation of autophagy.It has been reported that myotubularin family-PI 3-phosphatases, MTM1, MTMR3 and MTMR14 are involved in the regulation of autophagy in mammalian cells and that MTM3 plays a positive role in autophagosome maturation in C.elegans [1-4].It is conceivable that those phosphatases regulate autophagy by modulating the local PI3P level, e.g.on the surface of autophagosomes.However, it is largely unknown how and where their catalytic activities are exerted precisely.To address these issue, we tried to find the interacting proteins of MTMR3, which we previously reported as a regulator of autophaosome formation.