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 ho mology with a small heat shock protein, HSP27. Western blotting analyses sh owed that MKBP level in rat heart rapidly increased, with a sharp peak at o ne week after birth (3-fold the level at the fetus), but that it rapidly de creased (1/10 of peak value at 13 weeks). Human myocardium also showed simi lar age-dependency. Similar but small increase of HSP27 was observed in the neonatal rat myocardium, but not in constitutive and inducible forms of HS P70. Immunofluorescence analysis localized MKBP at the Z lines and intercal ated discs in the rat myocardium. MKBP may protect actin cytoskeleton or ot her proteins of heart muscle against oxidative stress in the neonate.