Nonselective cation channel probably playing a role in the regulation of membrane trafficking events. Acts as Ca(2+)-permeable cation channel with inwardly rectifying activity (PubMed:19763610). May activate ARF6 and be involved in the trafficking of GPI-anchored cargo proteins to the cell surface via the ARF6-regulated recycling pathway (By similarity). May play a role in immune processes. In adaptive immunity, TRPML2 and TRPML1 may play redundant roles in the function of the specialized lysosomes of B cells (PubMed:17050035). In the innate immune response, may play a role in the regulation of chemokine secretion and macrophage migration (PubMed:26432893). Through a possible and probably tissue-specific heteromerization with MCOLN1 may be at least in part involved in many lysosome-dependent cellular events. Channel activity is reduced by low extracellular/lumenal pH level. Forms homooligomeric complexes; probably tetrameric. Can heterooligomerize with MCOLN1; heteromeric assemblies have different channel properties as compared to the respective homooligomers and may be tissue-specific. Interacts with TMEM176A. Localizes to recycling endosomes in activated macrophages and microglia. Isoform 1 is widely expressed at very low levels. Isoform 2 is expressed at high levels in lymphoid tissues (thymus and spleen) and kidney, and at moderate levels in heart, lung, liver and stomach. Expressed in activated macrophages and microglia (at protein level). Up-regulated in microglia cells and macrophages by bacterial lipopolysaccharide (LPS). Up-regulated by infection with M.smegmatis. The most N-terminal extracellular/lumenal domain (referred to as I-II linker or polycystin-mucolipin domain) contributes to a structure with a four-fold rotational symmetry in a tetrameric assembly; the structure contains a central highly electronegative pore with a 14 A diameter. The pore is critical for Ca(2+) and pH regulation. The protruding structure formed by the I-II linkers may contain all the interaction sites with lipids and proteins in the endolysosomal lumen. No visible phenotype. The secretion of specific cytokines (CCL3, CCL5 and CXCL2) by macrophages exposed to bacterial lipopolysaccharide (LPS) is decreased. Mutant mice display decreased migration of macrophages into the intraperitoneal space after injection with LPS, or after infection with E.coli O78:H11 (strain H10407). Belongs to the transient receptor (TC 1.A.4) family. Polycystin subfamily. MCOLN2 sub-subfamily.