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Public A Mixed Periodic Paralysis & Myotonia Mutant, P1158S, Imparts pH-Sensitivity ... (2018) Ghovanloo et al

Discussion in 'Health News and Research unrelated to ME/CFS' started by merylg, Apr 25, 2018.

  1. merylg

    merylg Established Member (Voting Rights)

  2. Hutan

    Hutan Moderator Staff Member

    New Zealand

    Skeletal muscle channelopathies, many of which are inherited as autosomal dominant mutations, include myotonia and periodic paralysis. Myotonia is defined by a delayed relaxation after muscular contraction, whereas periodic paralysis is defined by episodic attacks of weakness.

    One sub-type of periodic paralysis, known as hypokalemic periodic paralysis (hypoPP), is associated with low potassium levels. Interestingly, the P1158S missense mutant, located in the third domain S4-S5 linker of the “skeletal muscle”, Nav1.4, has been implicated in causing both myotonia and hypoPP. A common trigger for these conditions is physical activity.

    We previously reported that Nav1.4 is relatively insensitive to changes in extracellular pH compared to Nav1.2 and Nav1.5. Given that intense exercise is often accompanied by blood acidosis, we decided to test whether changes in pH would push gating in P1158S towards either phenotype.

    Our results suggest that, unlike in WT-Nav1.4, low pH depolarizes the voltage-dependence of activation and steady-state fast inactivation, decreases current density, and increases late currents in P1185S. Thus, P1185S turns the normally pH-insensitive Nav1.4 into a proton-sensitive channel. Using action potential modeling we predict a pH-to-phenotype correlation in patients with P1158S.

    We conclude that activities which alter blood pH may trigger the noted phenotypes in P1158S patients.
  3. Amw66

    Amw66 Senior Member (Voting Rights)

    May explain lactate issues in subgroups?

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