Expression of scaffolding, signalling and contractile-filament proteins in human myometria: effects of pregnancy and labour

Successful parturition requires the co‐ordination of numerous myometrial signalling events to allow for timely and efficient uterine contractions. Late pregnancy and labour onset in humans may be associated with changes in the expression of myometrial proteins implicated in such uterine contractile signal integration. Accordingly, in myometria from non‐pregnant women and pregnant women, not in labour or in labour, we examined the content of putative plasmalemmal scaffolding proteins (caveolin‐1 and ‐2) and compared these to the proportions of signal transducing rho‐associated kinases (ROK α and β) and contractile filament‐associated proteins α‐actin, myosin regulatory light chain (MLC20) and h‐caldesmon. There was no effect of pregnancy or labour on the proportion of caveolin, ROK β or α‐actin. However, pregnancy was associated with a decrease in ROK α and MLC20 such that ROK α: α‐actin and MLC20: α‐actin ratios were reduced compared to myometria of non‐pregnant women. In contrast, h‐caldesmon was up‐regulated in pregnancy resulting in an elevated h‐caldesmon: α ‐actin ratio. There were, however, no further significant changes in ROK α, MLC20 or h‐caldesmon expression with spontaneous or oxytocin‐induced labour. These data suggest that the mechanism(s) integrating myometrial signalling events with the onset of human labour does not involve differential alterations of the cellular expressions of caveolins, ROK, α ‐actin, MLC20 or h‐caldesmon.

myometrium, pregnancy, labour, signalling molecules, smooth muscle

- 1. Challis J.R.G., Lye S.J., Parturition In: Knobil E., Neill JD., eds., The Physiology of Reproduction, edn.5, Raven Press; / New York , pp. 985–1031, 1994. [Google Scholar] - 2. Dalrymple A., Slater D.M., Poston L., Tribe R.M., Physiological induction of transient receptor potential canonical proteins, calcium entry channels, in human myometrium: influence of pregnancy, labor, and interleukin‐1, J. Clin. Endocrinol. Metab., 89: 1291–1300, 2004. [DOI] [PubMed] [Google Scholar] - 3. Taggart M.J., Menice C.B., Morgan K.G., Wray S., Effect of metabolic inhibition on intracellular Ca2+, phosphorylation of myosin regulatory light chain and force in rat smooth muscle, J. Physiol., 499: 485–496, 1997. [DOI] [PMC free article] [PubMed] [Google Scholar] - 4. Word R.A., Casey M.L., Kamm K.E., Stull J.T., Effects of cGMP on [Ca2+]i, myosin light chain phosphorylation, and contraction in human myometrium, Am. J. Physiol., 260: C861–867, 1991. [DOI] [PubMed] [Google Scholar] - 5. Taggart M.J., Wray S., Contribution of sarcoplasmic reticular calcium to smooth muscle contractile activation: gestational dependence in isolated rat uterus, J. Physiol., 511: 133–144, 1998. [DOI] [PMC free article] [PubMed] [Google Scholar] - 6. Lee Y.H., Hwang M.K., Morgan K.G., Taggart M.J., Receptor‐coupled contractility of uterine smooth muscle: from membrane to myofilaments, Exp. Physiol., 86: 283–288, 2001. [DOI] [PubMed] [Google Scholar] - 7. Sward K., Dreja K., Susnjar M., Hellstrand P., Hartshorne D.J., Walsh M.P., Inhibition of Rho‐associated kinase blocks agonist‐induced Ca2+ sensitization of myosin phosphorylation and force in guinea‐pig ileum, J. Physiol., 522: 33–49, 2000. [DOI] [PMC free article] [PubMed] [Google Scholar] - 8. Fujihara H., Walker L.A., Gong M.C., Lemichez E., Boquet P., Somlyo A.V., Somlyo A.P., Inhibition of RhoA translocation and calcium sensitization by in vivo ADP‐ribosylation with the chimeric toxin DC3B, Mol. Biol. Cell., 8: 2437–2447, 1997. [DOI] [PMC free article] [PubMed] [Google Scholar] - 9. Lucius C., Arner A., Steusloff A., Troschka M., Hofmann F., Aktories K., Pfitzer G., Clostridium difficile toxin B inhibits carbachol‐induced force and myosin light chain phosphorylation in guinea‐pig smooth muscle: role of Rho proteins, J. Physiol., 506: 83–93, 1998. [DOI] [PMC free article] [PubMed] [Google Scholar] - 10. Hartshorne D.J., Myosin phosphatase: subunits and interactions, Acta. Physiol. Scand., 164: 483–493, 1998. [DOI] [PubMed] [Google Scholar] - 11. Somlyo A.P., Somlyo A.V., Ca2+ sensitivity of smooth muscle and nonmuscle myosin II: modulated by G proteins, kinases, and myosin phosphatase, Physiol. Rev., 83: 1325–1358, 2003. [DOI] [PubMed] [Google Scholar] - 12. Sward K., Mita M., Wilson D.P., Deng J.T., Susnjar M., Walsh M.P., The role of RhoA and Rho‐associated kinase in vascular smooth muscle contraction, Curr. Hypertens. Rep., 5: 66–72, 2003. [DOI] [PubMed] [Google Scholar] - 13. Oh J.H., You S.K., Hwang M.K., Ahn D.S., Kwon S.C., Taggart M.J., Lee Y.H., Inhibition of Rho‐associated kinase reduces MLC20 phosphorylation and contractility of intact myometrium and attenuates agonist‐induced Ca2+ sensitization of force in permeabilized rat myometrium, J. Vet. Med. Sci., 65: 43–50, 2003. [DOI] [PubMed] [Google Scholar] - 14. Moran C.J., Friel A.M., Smith T.J., Cairns M., Morrison J.J., Expression and modulation of Rho kinase in human pregnant myometrium, Mol. Hum. Reprod., 8: 196–200, 2002. [DOI] [PubMed] [Google Scholar] - 15. Woodcock N.A., Taylor C.W., Thornton S., Effect of an oxytocin receptor antagonist and rho kinase inhibitor on the [Ca2+]i sensitivity of human myometrium, Am. J. Obstet. Gynecol., 190: 222–228, 2004. [DOI] [PubMed] [Google Scholar] - 16. Kupittayanant S., Burdyga T., Wray S., The effects of inhibiting Rho‐associated kinase with Y‐27632 on force and intracellular calcium in human myometrium, Pflugers Arch., 443: 112–114, 2001. [DOI] [PubMed] [Google Scholar] - 17. Taggart M.J., Leavis P., Feron O., Morgan K.G., Inhibition of PKC and rhoA translocation in differentiated smooth muscle by a caveolin scaffolding domain peptide, Exp. Cell. Res., 258: 72–81, 2000. [DOI] [PubMed] [Google Scholar] - 18. Taggart M.J., Smooth muscle excitation‐contraction coupling: a role for caveolae and caveolins News Physiol. Sci., 16: 61–65, 2001. [DOI] [PubMed] [Google Scholar] - 19. Feron O., Endothelial nitric oxide synthase expression and its functionality, Curr. Opin. Clin. Nutr. Metab. Care., 2: 291–296, 1999. [DOI] [PubMed] [Google Scholar] - 20. Parton R.G., Caveolae–from ultrastructure to molecular mechanisms, Nat. Rev. Mol. Cell. Biol., 4: 162–167, 2003. [DOI] [PubMed] [Google Scholar] - 21. Gingras D., Gauthier F., Lamy S., Desrosiers R.R., Beliveau R., Localization of RhoA GTPase to endothelial caveolae‐enriched membrane domains, Biochem. Biophys. Res. Commun., 247: 888–893, 1998. [DOI] [PubMed] [Google Scholar] - 22. Cornwell T.L., Li J., Sellak H., Miller R.T., Word R.A., Reorganization of myofilament proteins and decreased cGMP‐dependent protein kinase in the human uterus during pregnancy, J. Clin. Endocrinol. Metab., 86: 3981–3988, 2001. [DOI] [PubMed] [Google Scholar] - 23. MacDougall M.W., Europe‐Finner G.N., Robson S.C., Human myometrial quiescence and activation during gestation and parturition involve dramatic changes in expression and activity of particulate type II (RII) protein kinase A holoenzyme, J. Clin. Endocrinol. Metab., 88: 2194–2205, 2003. [DOI] [PubMed] [Google Scholar] - 24. Chanrachakul B., Matharoo‐Ball B., Turner A., Robinson G., Broughton‐Pipkin F., Arulkumaran S., Khan RN., Reduced expression of immunoreactive 2‐adrenergic receptor protein in human myometrium with labor, J. Clin. Endocrinol. Metab., 88: 4997–5001, 2003. [DOI] [PubMed] [Google Scholar] - 25. Moore F., Da Silva C., Wilde J.I., Smarason A., Watson SP., Lopez Bernal A., Up‐regulation of p21‐ and RhoA‐ activated protein kinases in human pregnant myometrium, Biochem. Biophys. Res. Commun., 269: 322–326, 2000. [DOI] [PubMed] [Google Scholar] - 26. Friel A.M., Ravikumar N., Smith T.J., Morrison J.J., RhoA and ROCK‐I protein levels in human myometrium during pregnancy, J. Soc. Gynecol. Invest., 11: 227A, 2004. [DOI] [PubMed] [Google Scholar] - 27. Word R.A., Stull J.T., Casey M.L., Kamm K.E., Contractile elements and myosin light chain phosphorylation in myometrial tissue from nonpregnant and pregnant women, J. Clin. Invest., 92: 29–37, 1993. [DOI] [PMC free article] [PubMed] [Google Scholar] - 28. Lipardi C., Mora R., Colomer V., Paladino S., Nitsch L., Rodriguez‐Boulan E., Zurzolo C., Caveolin transfection results in caveolae formation but not apical sorting of glycosylphosphatidylinositol (GPI)‐anchored proteins in epithelial cells, J. Cell. Biol., 140: 617–626, 1998. [DOI] [PMC free article] [PubMed] [Google Scholar] - 29. Ciray H.N., Guner H., Hakansson H., Tekelioglu M., Roomans G.M., Ulmsten U., Morphometric analysis of gap junctions in nonpregnant and term pregnant human myometrium, Acta. Obstet. Gynecol. Scand., 74: 497–504, 1995. [DOI] [PubMed] [Google Scholar] - 30. Obayashi HY., Word RA., Relationship between protein kinase C, caldesmon phosphorylation, and force generation in human myometrium during pregnancy, J. Soc. Gynecol. Invest., 10: 130A, 2003. [Google Scholar] - 31. Ozaki H., Yasuda K., Kim Y.S., Egawa M., Kanzaki H., Nakazawa H., Hori M., Seto M., Karaki H., Possible role of the protein kinase C/CPI‐17 pathway in the augmented contraction of human myometrium after gestation, Br. J. Pharmacol., 140: 1303–1312, 2003. [DOI] [PMC free article] [PubMed] [Google Scholar] - 32. Li Y., Je H.D., Malek S., Morgan K.G., ERK1/2‐mediated phosphorylation of myometrial caldesmon during pregnancy and labor, Am. J. Physiol. Regul. Integr. Comp. Physiol., 284: R192–199, 2003. [DOI] [PubMed] [Google Scholar] - 33. Marston S., Calcium ion‐dependent regulation of uterine smooth muscle thin filaments by caldesmon, Am. J. Obstet. Gynecol., 160: 252–257, 1989. [DOI] [PubMed] [Google Scholar] - 34. Europe‐Finner G.N., Phaneuf S., Mardon H.J., Lopez Bernal A., Human myometrial G s‐small (with serine) and Gs‐large (with serine) messenger ribonucleic acid splice variants promote the increased expression of 46‐ and 54‐ kilodalton G s protein isoforms in pregnancy and their downregulation during labor, J. Clin. Endocrinol. Metab., 81: 1069–1075, 1996. [DOI] [PubMed] [Google Scholar] - 35. Chanrachakul B., Matharoo‐Ball B., Turner A., Robinson G., Broughton‐Pipkin F., Arulkumaran S., Khan RN., Immunolocalization and protein expression of the α ‐subunit of the large‐conductance calcium‐activated potassium channel in human myometrium, Repord., 126: 43–48, 2003. [DOI] [PubMed] [Google Scholar] - 36. Matharoo‐Ball B., Ashford M.L., Arulkumaran S., Khan R.N., Down‐regulation of the α ‐ and β ‐subunits of the calcium‐activated potassium channel in human myometrium with parturition, Biol. Reprod., 68: 2135–2141, 2003. [DOI] [PubMed] [Google Scholar]