抄録
Background and Objectives: Laminin, which is a major component of the extracellular matrix, is known to increase in the myocytes in the diabetic heart and dilated cardiomyopathy. The laminin gamma 1 chain promoter contains a transcriptional element denoted bcn-1 that is inducible and active (Suzuki H, et al. J Biol Chem 271:1996). To elucidate the molecular pathogenesis of the increase of laminin in the cardiac muscle cells of cardiomyopathy, we have carried out the yeast one-hybrid screen using bcn-1 as a bait, and cloned Smarce 1r protein as a molecular partner which interacts with bcn-1 protein. Next, we repeated two-hybrid screen using Smarce 1r as a bait and cloned MLF11P as a partner (Suzuki H, Exp Clin Cardiol 9:2004).Methods: The yeast two-hybrid screen analysis was carried out again using MLF11P protein (amino-acids 1-318) as a bait. A human heart cDNA library was screened by the yeast mating method for overnight culture.Results: We isolated two final positive clones encoded the same protein, which is an alternative-RNA splicing form of the human cardiac troponin I (TnI) protein and we call this as a spliced form of TNI (STNI). The mRNA expression pattern of STNI is heart-specific. The STNI shares several sequence similarities with the human cardiac TNI but lacks troponin T binding protein.Conclusions: We report the heart-specific segment of the human cardiac troponin I isoform which lacks troponin C binding portion. These results suggest that STNI might be involved in the molecular pathogenesis of the increase of laminin in the cardiomyopathy. [J Physiol Sci. 2006;56 Suppl:S53]
