Myosin light chain kinase and the onset of labour in humans

Myosin light chain kinase (MLCK) is essential for myometrial contractions i nduced by calcium-mobilizing agonists. From the gene of vertebrate smooth m uscle/non-muscle MLCK there are at least four proteins expressed. We have f ound that both a >200 and a 137 kDa MLCK are equally expressed in human non -pregnant (NP) and term pregnant (P) uterine smooth muscle and confirmed th at 19 kDa telokin (TK) is only expressed in P myometrium. In addition, we h ave observed that a MLCK immunogen at similar to 60 kDa is only expressed i n NP myometrium, suggesting that its expression is inhibited during normal pregnancy in a hormonally dependent manner. However, when a e compared preg nant myometrium from patients delivered preterm (PT) (< 34 weeks gestation) , but not in labour (NIL), with PT patients in labour (IL) we found that PT (IL) samples expressed the <similar to>60 kDa MLCK immunogen and thus displ ayed a NP phenotype whereas PT(ML) samples did not express the protein and retained a pregnant phenotype. We hypothesize that the novel similar to 60 kDa MLCK immunogen contributes to the aberrent contractility associated wit h preterm labour.