This gene encodes a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase that functions as a tumor suppressor, frequently mutated in various cancers. The protein contains a tensin-like domain and a catalytic domain similar to dual specificity protein tyrosine phosphatases, but preferentially dephosphorylates phosphoinositide substrates. It regulates AKT/PKB signaling by decreasing phosphatidylinositol-3,4,5-trisphosphate levels. A non-canonical initiation site produces a longer isoform, potentially involved in regulating mitochondrial energy metabolism. A pseudogene exists on chromosome 9. Alternative splicing and multiple start codons generate different isoforms of the protein.