Functional characterization of the type 1 inositol 1,4,5-trisphosphate receptor coupling domain SII(+/-) splice variants and the Opisthotonos mutant form

Biophys J. 2002 Apr;82(4):1995-2004. doi: 10.1016/S0006-3495(02)75548-3.

Abstract

The type 1 inositol (1,4,5)-trisphosphate receptor (InsP3R1) plays a critical role in Ca2+ signaling in cells. Neuronal and nonneuronal isoforms of the InsP3R1 differ by alternative splicing in the coupling domain of the InsP3R1 (SII site). Deletion of 107 amino acids from the coupling domain of the InsP3R1 results in epileptic-like behaviors in opisthotonos (opt) spontaneous mouse mutant. Using Spodoptera frugiperda cells expression system, we compared single-channel behavior of recombinant InsP3R1-SII(+), InsP3R1-SII(-), and InsP3R1-opt channels in planar lipid bilayers. The main results of our study are: 1) the InsP3R1-SII(-) has a higher conductance (94 pS) and the InsP3R1-opt has a lower conductance (64 pS) than the InsP3R1-SII(+) (81 pS); 2) the bell-shaped Ca2+-dependence peaks at 200-300 nM Ca2+ for all three InsP3R1 isoforms; 3) the bell-shaped Ca2+-dependence is wider for the InsP3R1-SII(+) and narrower for the InsP3R1-SII(-) and InsP3R1-opt; 4) the apparent affinity for ATP is sixfold lower for the InsP3R1-SII(-) (1.4 mM) and 20-fold lower for the InsP3R1-opt (5.3 mM) than for the InsP3R1-SII(+) (0.24 mM); 5) the InsP3R1-SII(-) is approximately twofold more active than the InsP3R1-SII(+) in the absence of ATP. Obtained results provide novel information about the molecular determinants of the InsP3R1 function.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Allosteric Site
  • Alternative Splicing*
  • Animals
  • Calcium / metabolism
  • Calcium Channels / chemistry*
  • Calcium Channels / metabolism*
  • Cell Line
  • Chickens
  • Cytosol / metabolism
  • Electrophysiology
  • Inositol 1,4,5-Trisphosphate Receptors
  • Insecta
  • Mice
  • Microsomes / metabolism
  • Models, Genetic
  • Mutation*
  • Phenotype
  • Protein Structure, Tertiary
  • Rats
  • Receptors, Cytoplasmic and Nuclear / chemistry*
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Spodoptera / metabolism
  • Time Factors

Substances

  • Calcium Channels
  • Inositol 1,4,5-Trisphosphate Receptors
  • Receptors, Cytoplasmic and Nuclear
  • Recombinant Proteins
  • Adenosine Triphosphate
  • Calcium