Transient up-regulation of myotonic dystrophy protein kinase-binding protein, MKBP, and HSP27 in the neonatal myocardium.

Myotonic dystrophy protein kinase (DMPK)-binding protein, MKBP, has high homology with a small heat shock protein, HSP27. Western blotting analyses showed that MKBP level in rat heart rapidly increased, with a sharp peak at one week after birth (3-fold the level at the fetus), but that it rapidly decreased (1/10 of peak value at 13 weeks). Human myocardium also showed similar age-dependency. Similar but small increase of HSP27 was observed in the neonatal rat myocardium, but not in constitutive and inducible forms of HSP70. Immunofluorescence analysis localized MKBP at the Z lines and intercalated discs in the rat myocardium. MKBP may protect actin cytoskeleton or other proteins of heart muscle against oxidative stress in the neonate.