Altered Expression of Human Smooth Muscle Myosin Phosphatase Targeting (MYPT) Isovariants with Pregnancy and Labor

Abstract

BackgroundMyosin light-chain phosphatase is a trimeric protein that hydrolyses phosphorylated myosin II light chains (MYLII) to cause relaxation in smooth muscle cells including those of the uterus. A major component of the phosphatase is the myosin targeting subunit (MYPT), which directs a catalytic subunit to dephosphorylate MYLII. There are 5 main MYPT family members (MYPT1 (PPP1R12A), MYPT2 (PPP1R12B), MYPT3 (PPP1R16A), myosin binding subunit 85 MBS85 (PPP1R12C) and TIMAP (TGF-beta-inhibited membrane-associated protein (PPP1R16B)). Nitric oxide (NO)-mediated smooth muscle relaxation has in part been attributed to activation of the phosphatase by PKG binding to a leucine zipper (LZ) dimerization domain located at the carboxyl-terminus of PPP1R12A. In animal studies, alternative splicing of PPP1R12A can lead to the inclusion of a 31-nucleotide exonic segment that generates a LZ negative (LZ-) isovariant rendering the phosphatase less sensitive to NO vasodilators and alterations in PPP1R12ALZ- and LZ+ expression have been linked to phenotypic changes in smooth muscle function. Moreover, PPP1R12B and PPP1R12C, but not PPP1R16A or PPP1R16B, have the potential for LZ+/LZ- alternative splicing. Yet, by comparison to animal studies, the information on human MYPT genomic sequences/mRNA expressions is scant. As uterine smooth muscle undergoes substantial remodeling during pregnancy we were interested in establishing the patterns of expression of human MYPT isovariants during this process and also following labor onset as this could have important implications for determining successful pregnancy outcome.ObjectivesWe used cross-species genome alignment, to infer putative human sequences not available in the public domain, and isovariant-specific quantitative PCR, to analyse the expression of mRNA encoding putative LZ+ and LZ- forms of PPP1R12A, PPP1R12B and PPP1R12C as well as canonical PPP1R16A and PPP1R16B genes in human uterine smooth muscle from non-pregnant, pregnant and in-labor donors.ResultsWe found a reduction in the expression of PPP1R12A, PPP1R12BLZ+, PPP1R16A and PPP1R16B mRNA in late pregnancy (not-in-labor) relative to non-pregnancy. PPP1R12ALZ+ and PPP1R12ALZ- mRNA levels were similar in the non-pregnant and pregnant not in labor groups. There was a further reduction in the uterine expression of PPP1R12ALZ+, PPP1R12CLZ+ and PPP1R12ALZ- mRNA with labor relative to the pregnant not-in-labor group. PPP1R12A, PPP1R12BLZ+, PPP1R16A and PPP1R16B mRNA levels were invariant between the not in labor and in-labor groups.ConclusionsMYPT proteins are crucial determinants of smooth muscle function. Therefore, these alterations in human uterine smooth muscle MYPT isovariant expression during pregnancy and labor may be part of the important molecular physiological transition between uterine quiescence and activation.

Genomic study and Medical Subject Headings enrichment analysis of early pregnancy rate and antral follicle numbers in Nelore heifers1,2

“…Protein phosphatase 1 regulatory subunit 12B (PPP1R12B) may be involved with insulin signaling (Pham et al, 2012). This gene is associated with smooth muscle contractibility and regulation of uterine cell hypertrophy in the early stages of gestation (Lartey et al, 2016). Ryu et al (2016) found that PPP1R12B participates in protein phosphorylation, which may influence reproduction in humans.…”

New susceptibility alleles associated with severe coronary artery stenosis in the Lebanese population

“…PPP1R12A, located 9.7 kb downstream of rs17005877, is involved in the expression of light-chain myosin phosphatase. This protein belongs to the family of myosin targeting subunit (MYPT), which is involved in the regulation of light chain myosin phosphatase recently implicated in the aberrant contractility associated with atherosclerosis [40][41][42].…”

Proteomic Analysis of Uterine Tissues During Peri-Implantation Period in Mice with Experimentally Induced Adenomyosis that Treated with anti-Ngf: Implications for Cell-Cell Adhesion and Metabolic Processes

“…PIK3CA was found participated in the process of gland development and epithelial cell invasiveness, which are of great importance in the pathology of adenomyosis [ 35 ] [ 36 ]. PPP1R12C and PPP1R12B are the main members of myosin-targeting subunit (MYPT), which is a major component of the phosphatase and a crucial determinant of function of smooth muscle cells [ 37 ]. In the present study, the low expression levels of PPP1R12C and PPP1R12B were partly related to the myometrium injury in adenomyosis, and anti-NGF therapy might be advantageous for repair of myometrial defect.…”