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Functional Characterization of Endogenously Expressed Human RYR1 Variants
07:59

Functional Characterization of Endogenously Expressed Human RYR1 Variants

Published on: June 9, 2021

Dynamic regulation of ryanodine receptor type 1 (RyR1) channel activity by Homer 1

Wei Feng1, Jiancheng Tu, Pierre Pouliquin

  • 1Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. fengwei@ucdavis.edu

Cell Calcium
|August 21, 2007
PubMed

Insights

Homer 1 (H1) proteins regulate skeletal muscle ryanodine receptor type 1 (RyR1) channel activity. Both long and short H1 forms modulate RyR1 binding, with combined effects dependent on total H1 concentration.

Area of Science:

  • Muscle physiology
  • Molecular biology
  • Protein interactions

Background:

  • Homer proteins, initially found in neurons, are also present in skeletal muscle.
  • Homer 1 (H1) splice variants influence the ryanodine receptor type 1 (RyR1) channel complex.
  • Understanding H1 regulation of RyR1 is crucial for skeletal muscle function.

Purpose of the Study:

  • To investigate the distinct and combined actions of Homer 1 (H1) long and short splice variants on ryanodine receptor type 1 (RyR1) channel activity.
  • To elucidate the concentration-dependent effects of H1 forms on RyR1 conformation and function.

Main Methods:

  • Utilized [3H]ryanodine binding assays to assess RyR1 conformational states.
  • Examined the effects of H1 long-forms (H1b, H1c) and short-forms (H1a, H1EVH1) individually and in combination.
  • Reconstituted purified RyR1 channels in planar lipid bilayers to study H1 regulation.

Main Results:

  • Both H1 long-forms and short-forms enhanced [3H]ryanodine binding to RyR1 at concentrations <= 200 nM.
  • At concentrations > 200 nM, all H1 forms inhibited [3H]ryanodine binding.
  • Combinations of H1 variants (e.g., H1c+H1EVH1) exhibited additive effects on RyR1 binding, with net regulation dependent on total H1 concentration.
  • H1a and H1c demonstrated similar dynamic regulatory patterns on purified RyR1 channels.

Conclusions:

  • Homer 1 (H1) proteins, through their long and short splice variants, provide a flexible mechanism for regulating skeletal muscle RyR1 channel activity.
  • The concentration of total H1 dictates whether RyR1 activity is enhanced or inhibited.
  • These findings offer insight into how dynamic changes in H1 expression levels fine-tune RyR1 channel function in skeletal muscle.

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