Inositol 1,4,5-trisphosphate receptor type 2 (ITPR2), also known as IP3 receptor subtype 2, is a ligand-gated calcium release channel located in the endoplasmic reticulum (ER) membrane that mediates the release of calcium ions into the cytoplasm in response to second messenger signaling. [1] ITPR2 belongs to the IP3 receptor family, a group of large tetrameric channels (approximately 270 kDa per subunit) that form calcium release channels in the ER membrane. Each functional channel consists of four subunits, each containing six transmembrane domains and a large cytoplasmic regulatory domain that binds inositol 1,4,5-trisphosphate (IP3), the second messenger generated by phospholipase C activation. [2]
Calcium release through ITPR2 is a fundamental signaling mechanism in virtually all cell types, regulating synaptic plasticity, neuronal excitability, gene expression, and countless other calcium-dependent processes. [3] Dysregulation of ITPR2-mediated calcium signaling has been implicated in Alzheimer's disease, Parkinson's disease, Huntington's disease, and various cancers where calcium signaling pathways are often dysregulated. [4][5]
| ITPR2 Protein | |
|---|---|
| Protein Name | Inositol 1,4,5-Trisphosphate Receptor Type 2 |
| Gene | [ITPR2](/genes/itpr2) |
| UniProt ID | [Q14571](https://www.uniprot.org/uniprot/Q14571) |
| Molecular Weight | ~270 kDa per subunit |
| Subcellular Localization | Endoplasmic Reticulum |
| Protein Family | IP3 receptor family (ITPR1, ITPR2, ITPR3) |
| Tissue Distribution | High in brain (cerebellum, hippocampus), pancreas, lung |
ITPR2 has a characteristic IP3 receptor structure:
N-terminal ligand-binding domain: The large cytoplasmic domain (approximately 2000 residues) that binds IP3 with high affinity. This domain contains the "IP3-binding core" and is the target for regulatory proteins.
Modulatory domain: Located between the binding domain and the transmembrane region, this region contains binding sites for various regulatory proteins including calmodulin and FKBP12.
Transmembrane domain: Six hydrophobic segments (M1-M6) that form the ion channel pore. The M1-M4 segments form the voltage sensor-like domain, while M5 and M6 along with the pore loop between them form the channel pore.
C-terminal channel domain: Contains the channel pore and regulatory elements including the Ca²⁺ binding site that modulates channel activity.
ITPR2 forms a tetrameric channel with the following properties:
ITPR2 undergoes several important post-translational modifications:
ITPR2 mediates calcium-induced calcium release (CICR), a fundamental signaling mechanism where initial Ca²⁺ release triggers further release, amplifying the calcium signal. This process is crucial in:
In neurons, ITPR2 plays a critical role in synaptic plasticity:
ITPR2 contributes to neuronal excitability through:
Ca²⁺ release through ITPR2 activates:
ITPR2 participates in cellular calcium homeostasis:
ITPR2 dysfunction is strongly implicated in Alzheimer's disease pathogenesis:
The "calcium dysregulation hypothesis" of AD proposes that altered calcium signaling is an early event in disease progression. [4:1] ITPR2 contributes to this through:
Amyloid-beta oligomers directly interact with ITPR2:
Tau pathology affects ITPR2 function:
Restoring ITPR2 function is a promising therapeutic strategy:
ITPR2 alterations contribute to dopaminergic neuron degeneration:
ITPR2-mediated Ca²⁺ release links to mitochondrial dysfunction:
Alpha-synuclein affects ITPR2 function:
ITPR2 modulators may benefit PD:
ITPR2 is profoundly affected in Huntington's disease:
ITPR2 alterations in striatal neurons:
Mutant huntingtin protein affects ITPR2:
ITPR2 dysfunction is implicated in:
ITPR2 shows tissue-specific expression:
ITPR2 interacts with numerous proteins:
| Protein | Interaction | Functional Effect |
|---|---|---|
| Homer | Scaffold | Anchors ITPR to postsynaptic density |
| RyR | Calcium release | Coordinates calcium signaling |
| Calmodulin | Calcium sensing | Modulates channel activity |
| FKBP12 | Immunophilin | Regulates gating |
| BAP31 | ER chaperone | Involved in trafficking |
| mGluR1/5 | GPCR signaling | Couples to IP3 production |
| Compound | Target | Development Stage |
|---|---|---|
| Xestospongin C | ITPR antagonist | Research |
| 2-APB | ITPR modulator | Research |
| Caffeine | RyR/ITPR activator | Clinical use |
Current research focuses on:
Furuichi T, Simon-Chazottes D, Fujino I, et al. Cloning and expression of a novel inositol 1,4,5-trisphosphate receptor subtype, IP3R-2. Nature. 1993. ↩︎
Bezprozvanny I, Watras J, Ehrlich BE. Bell-shaped calcium-response curves of Ins(1,4,5)P3- and calcium-gated channels from endoplasmic reticulum of cerebellum. Nature. 1991. ↩︎ ↩︎
Mikoshiba K. Inositol 1,4,5-trisphosphate receptor. Trends in Pharmacological Sciences. 1995. ↩︎
Stutzmann GE, LaFerla FM. Calcium dysregulation in Alzheimer's disease: from synaptic plasticity to cellular homeostasis. Neurobiology of Aging. 2007. ↩︎ ↩︎
Bhattacharya S, Zhao Y, Ding Y, et al. IP3 receptor heterogeneity and altered calcium signaling in Alzheimer's disease. Journal of Alzheimer's Disease. 2018. ↩︎ ↩︎
Popugaeva E, Pchitskaya E, Bezprozvanny I. Restore of IP3 signaling as a therapeutic approach for neurodegenerative diseases. International Journal of Molecular Sciences. 2017. ↩︎
Linde CI, Kang J, Feng J, et al. Parkinson's disease mutations in ITPR2 and calcium signaling. Cell Calcium. 2018. ↩︎
Selvaraj S, Sun Y, Singh BB. Calcium signaling and neurodegenerative diseases. Cell Calcium. 2019. ↩︎