Transgenesis based on organ specific gene expression has provided the basis to 
elucidate the functional role of proteins for the past 15 years. Using this 
technology, we showed that inhibition of the protein phosphatase 1, by its 
constitutively active inhibitor-1, significantly increases cardiac contractility 
and calcium handling. To uncover protein changes accompanying the chronic 
increases in cardiac function of these transgenic hearts, we analyzed the 
cardiac proteome. Interestingly, we found significant increases in the levels of 
6 proteins involved in metabolism, calcium binding and scavenging of 
oxido-reductive stress. These proteins were identified as: hydroxyacyl CoA 
dehydrogenase II, alpha subunit of the mitochondrial proton ATPase, 
peroxiredoxin 2, a novel EF-hand containing protein-2, annexin 5, and a 
previously uncharacterized cDNA. Thus, long-term cardiac specific overexpression 
of the protein phosphatase 1 inhibitor-1 and the associated increases in cardiac 
contractility appear to herald changes in a rather small number of proteins, 
which may reflect important compensatory adaptations in a hyperdynamic heart 
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