PPM1M is a serine/threonine protein phosphatase belonging to the metal-dependent PPM (PP2C) family that binds manganese and magnesium ions in its catalytic center to dephosphorylate target proteins 1. As a member of the PPM1H/PPM1J/PPM1M phylogenetic class, PPM1M functions as a single-subunit enzyme with a conserved catalytic core containing metal-chelating residues 1. PPM1M exhibits substrate selectivity, preferentially dephosphorylating phosphorylated Rab12 (phosphoRab12) while also acting on phosphoRab8A and phosphoRab10 2. This activity positions PPM1M as a key regulator of the LRRK2 signaling pathway, which controls receptor trafficking through Rab GTPase phosphorylation 2. Functionally, PPM1M participates in cellular processes including control of cilia biology—PPM1M knockout leads to primary cilia loss in striatal interneurons 2. Disease relevance includes Parkinson's disease, where rare PPM1M mutations showing catalytic inactivity have been identified in patients 2. Beyond neurological disorders, PPM1M demonstrates involvement in viral pathogenesis, with PPM1M downregulation inhibiting HSV-1 replication in astrocytes 3. In cancer contexts, PPM1M expression is typically reduced in tumors versus normal tissues and correlates with patient prognosis and tumor immune infiltration patterns 4, suggesting potential immunological and prognostic significance.