Cytohesins in the heart: their expression and interaction with the natriuretic peptide system

Natriuretic peptides (NPs) are cardiac hormones that play a significant role in functioning of the heart and are promising for treatment of heart failure. NPs increase cGMP levels by activating two NP receptors, NPR-A (ANP and BNP) and NPR-B (CNP). However, the influence of these two receptors on contractility and various intracellular targets is not the same. Our aim is to study if activity of NPRs is differentially regulated by the interacting proteins, cytohesins.

By Western blotting and qPCR we found that cytohesins 1-4 were expressed in rat and mouse ventricular cardiomyocytes, in several cardiac cell lines and in different compartments of the rat heart. Besides, we observed that expression of cytohesin-3 and -4 was significantly altered in a rat heart failure model. Using co-immunoprecipitation and microscale thermophoresis, we demonstrated that cytohesin-2 and -4 interacted with both NPR-A and NPR-B. Using peptide array assay, we identified peptide sequences from the NPRs that were involved in the interaction. Furthermore, the cytohesin inhibitor SecinH3 significantly altered the levels of cGMP produced by the two NPRs in rat ventricular cardiomyocytes and several cell lines. Finally, we found that SecinH3 reduced the CNP-induced negative inotropic response but enhanced its lusitropic effect in the isolated rat left ventricular muscle strips.

These results provide novel information about the expression of cytohesins in the heart and their connection to the natriuretic peptide system, supporting our hypothesis that cytohesins may be involved in regulation of the natriuretic peptide receptors activity.