The expression of P-Ser16 HspB6 in uterine smooth muscle during pregnancy

Abstract

The small heat shock protein HspB6 has been associated with smooth muscle relaxation when phosphorylated at amino acid serine-16 (P-Ser16). P-Ser16 HspB6 expression has not been previously determined in the myometrium during normal pregnancy and labour, periods of uterine quiescence and contraction, respectively. P-Ser16-HspB6 expression in the rat myometrium significantly increased during late pregnancy and labour (One-way ANOVA; p<0.05) and decreased significantly postpartum. At late pregnancy, expression of P-Ser16 HspB6 in a unilateral pregnancy model was increased in the gravid horn compared to the empty horn by immunoblot analysis. Immunoblot analysis also showed that 17β-Estradiol significantly increased P-Ser16 HspB6 expression in a 17β-Estradiol administration model compared to vehicle controls (Two-way ANOVA; p<0.05). Thus, 17β-Estradiol and uterine stretch positively regulate post-translational phosphorylation of HspB6. Finally, studies with the M-11 myometrial cell line demonstrated that HspB6 was localized in the cytoplasm, while P-Ser16 HspB6 was primarily localized in the nucleus under standard tissue culture conditions.