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Phasic phosphorylation of caldesmon and ERK 1/2 during contractions in human myometrium

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posted on 2025-05-09, 07:55 authored by Jonathan PaulJonathan Paul, Kaushik Maiti, Mark Read, Alexis HureAlexis Hure, Julia Smith, Eng-Cheng Chan, Roger SmithRoger Smith
Human myometrium develops phasic contractions during labor. Phosphorylation of caldesmon (h-CaD) and extracellular signal-regulated kinase 1/2 (ERK 1/2) has been implicated in development of these contractions, however the phospho-regulation of these proteins is yet to be examined during periods of both contraction and relaxation. We hypothesized that protein phosphorylation events are implicated in the phasic nature of myometrial contractions, and aimed to examine h-CaD and ERK 1/2 phosphorylation in myometrium snap frozen at specific stages, including; (1) prior to onset of contractions, (2) at peak contraction and (3) during relaxation. We aimed to compare h-CaD and ERK 1/2 phosphorylation in vitro against results from in vivo studies that compared not-in-labor (NIL) and laboring (L) myometrium. Comparison of NIL (n = 8) and L (n = 8) myometrium revealed a 2-fold increase in h-CaD phosphorylation (ser-789; P = 0.012) during onset of labor in vivo, and was associated with significantly up-regulated ERK2 expression (P = 0.022), however no change in ERK2 phosphorylation was observed (P = 0.475). During in vitro studies (n = 5), transition from non-contracting tissue to tissue at peak contraction was associated with increased phosphorylation of both h-CaD and ERK 1/2. Furthermore, tissue preserved at relaxation phase exhibited diminished levels of h-CaD and ERK 1/2 phosphorylation compared to tissue preserved at peak contraction, thereby producing a phasic phosphorylation profile for h-CaD and ERK 1/2. h-CaD and ERK 1/2 are phosphorylated during myometrial contractions, however their phospho-regulation is dynamic, in that h-CaD and ERK 1/2 are phosphorylated and dephosphorylated in phase with contraction and relaxation respectively. Comparisons of NIL and L tissue are at risk of failing to detect these changes, as L samples are not necessarily preserved in the midst of an active contraction.

History

Journal title

PLoS ONE

Volume

6

Issue

6

Publisher

Public Library of Science

Language

  • en, English

College/Research Centre

Faculty of Health

School

School of Medicine and Public Health

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