Calcium channel mediating constitutive calcium ion entry. Its activity is increased by reduction in extracellular osmolarity, by store depletion and muscarinic receptor activation. In addition, forms heteromultimeric ion channels with TRPM1 which are permeable for calcium and zinc ions (PubMed:21278253). Interacts with TRPM1; the interaction results in the formation of a heteromultimeric cation channel complex. Expressed primarily in the kidney and, at lower levels, in brain, testis, ovary, pancreas and spinal cord. Expression in the brain and kidney was determined at protein level. In the kidney, expressed predominantly in the collecting tubular epithelium in the medulla, medullary rays, and periglomerular regions; in the brain, highest levels are found in the cerebellum, choroid plexus, the locus coeruleus, the posterior thalamus and the substantia nigra. Down-regulated in renal tumors compared to normal kidney. Belongs to the transient receptor (TC 1.A.4) family. LTrpC subfamily. TRPM3 sub-subfamily. Cloning artifact in C-terminus.