The ITPR1 gene encodes the receptor for inositol 1,4,5-triphosphate, a messenger produced by phospholipase C. The ITPR1 receptor is an intracellular ligand-gated calcium channel, and upon activation by inositol 1,4,5-triphosphate, it mediates the release of calcium ions from the endoplasmic reticulum. By carrying out its function, ITPR1 plays a role in calcium-mediated signaling, ER-stress induced apoptosis, platelet activation, insulin secretion and cardiac conduction.

The ITPR1 protein consists of a transmembrane domain near the C terminal, an inositol triphosphate binding domain near the N terminal and a coupling domain in the middle of the molecule. It also consists of at least 2 consensus protein kinase A phosphorylation sites and at least 1 consensus ATP-binding site. The gene has been associated with Spinocerebellar Ataxia 15 (SCA15, autosomal dominant), Spinocerebellar Ataxia 29 (SCA29) and Gillespie Syndrome.

ITPR1 mRNA is ubiquitously expressed, and is thought to translate locally in neuronal cells through cis and trans effectors in response to synaptic activity. Protein is widely expressed and exists in multiple isoforms with one isoform mainly functioning in the brain; peripheral protein expression is most abundant in blood mononuclear cells, urine, lung alveolar lavage, and colon. 8 possible alternatively spliced isoforms and 5 paralogs have been identified. ITPR1 exhibits an N-terminal ligand binding (inositol triphosphate) domain, coupling and modulatory domain, a C-terminal multi-pass transmembrane (calcium channel) domain, as well as kinase phosphorylation and ATP-binding sites. Inositol triphosphate binds and homotetramerizes ITPR1 and mediates the flow of Ca⁺² ions from endoplasmic reticulum, cytosolic, or vesicular calcium stores.  

ITPR1 haploinsufficiency is associated with multiple autosomal dominant disorders. Large heterozygous deletions in ITPR1 are mainly associated with spinocerebellar ataxia 15 (SCA15); heterozygous missense mutations are associated with spinocerebellar ataxia 29 (SCA29), as well as rare cases of SCA15. Heterozygous missense and in frame deletion mutations are associated with Gillespie Syndrome.