Phosphatase that acts on various phosphoinositides, including phosphatidylinositol 4-phosphate, phosphatidylinositol (4,5)-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate (By similarity). Has a role in clathrin-mediated endocytosis (By similarity). Hydrolyzes PIP2 bound to actin regulatory proteins resulting in the rearrangement of actin filaments downstream of tyrosine kinase and ASH/GRB2 (By similarity). a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + phosphate Interacts with ASH/GRB2. Interacts with PACSIN1, PACSIN2 and PACSIN3 (PubMed:11082044). Binds AMPH, SH3GL1, SH3GL2 and SH3GL3. Interacts with MYO1E (via SH3 domain). Interacts with BIN1 and DNM1 (By similarity). Binds to EPS15 (a clathrin coat-associated protein) via a C-terminal domain containing three Asn-Pro-Phe (NPF) repeats. The C-terminal proline-rich region mediates binding to a variety of SH3 domain-containing proteins including AMPH, SH3GL1, SH3GL2, SH3GL3 and GRB2. Belongs to the synaptojanin family. In the central section; belongs to the inositol 1,4,5-trisphosphate 5-phosphatase family.