ITPR2 (Inositol 1,4,5-trisphosphate Receptor Type 2) is a large intracellular calcium release channel located primarily on the endoplasmic reticulum (ER) membrane. As a member of the IP3 receptor family, ITPR2 plays a fundamental role in cellular signaling by mediating the release of calcium ions from ER stores in response to various extracellular and intracellular stimuli[@bezprozvanny2009].
Calcium signaling is essential for numerous neuronal functions including synaptic transmission, gene expression, mitochondrial function, and cellular survival. Dysregulation of calcium homeostasis is a hallmark of many neurodegenerative diseases, making ITPR2 a critical protein in understanding the molecular basis of neurodegeneration[@mattson2012].
Structure
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ITPR2 — Inositol 1,4,5-Trisphosphate Receptor Type 2
ITPR2 (Inositol 1,4,5-trisphosphate Receptor Type 2) is a large intracellular calcium release channel located primarily on the endoplasmic reticulum (ER) membrane. As a member of the IP3 receptor family, ITPR2 plays a fundamental role in cellular signaling by mediating the release of calcium ions from ER stores in response to various extracellular and intracellular stimuli[@bezprozvanny2009].
Calcium signaling is essential for numerous neuronal functions including synaptic transmission, gene expression, mitochondrial function, and cellular survival. Dysregulation of calcium homeostasis is a hallmark of many neurodegenerative diseases, making ITPR2 a critical protein in understanding the molecular basis of neurodegeneration[@mattson2012].
Structure
Domain Architecture
ITPR2 is a massive ~3000 amino acid protein forming a tetrameric channel complex. Each subunit contains:
N-terminal ligand-binding domain: Contains the IP3 binding site and regulatory elements
Modulatory domain: Multiple regulatory sites for calcium, ATP, and protein kinases
Transmembrane domain: Six membrane-spanning helices forming the ion conductance pore
C-terminal channel domain: Forms the Ca²⁺ conducting pore and regulatory tail
Structural Features
The IP3 binding domain comprises a "armadillo repeat" fold that undergoes conformational changes upon IP3 binding, leading to channel opening. The channel pore is formed by the six transmembrane helices with a selectivity filter determining ion specificity. The C-terminal tail contains a calcium-binding EF-hand domain that modulates channel activity in response to intracellular calcium concentrations.
Molecular Function
Calcium Release Mechanism
ITPR2 functions as a ligand-gated calcium release channel:
Activation: Binding of inositol 1,4,5-trisphosphate (IP3) to the N-terminal ligand-binding domain