Abstract 900: αlpha-Actinin2-LIM Domain Protein Interactions, a Mechano-Sensitive Signaling Pathway Involved in Cardiomyopathies
Background: The Z-line is a highly specialized structure of the striated muscle that anchors the contractile filaments and maintains the sarcomere integrity between contraction-relaxation cycles. Recent studies suggest that Z-line is involved in sensoring cardiomyocyte mechano-stretch signaling, but the mechanisms associated with this process are unknown. α-Actinin2 is a major protein of the Z-line by playing a key role in the formation of a interactive net of signaling proteins including LIM domain protein, kinases and phosphatases.
Objetive: To study the role of α-Actinin2 and its LIM domain binding protein partners ZASP, Zyxin and MLP in mechano-stretch signaling pathways.
Methods: Mouse model and cardiomyocyte cell line, both overexpressing the human ZASP-1 isoform and the α-actinin2 DCM-associated mutation (Q9R-α-Actinin-2) were characterized by immunohistochemistry, Western blot analysis, immunoprecipitation, microarray and Northern blot analysis to explore the role of α-Actinin2-LIM domains dependent protein interactions and signaling pathways.
Results: In culture cardiomyocyte α-Actinin2, localized at focal adhesion with MLP, Zyxin and ZASP and translocate to the nuclei in response to mechanical stimulation induced by short period of cyclic stretch. DCM mutants Q9R-Actinin2 do not translocates to the nucleus in respond to either cyclic stretch or Leptomycin B. Mice carrying the Q9R-Actinin2 mutation develop cardiomyopathy and show activation of focal adhesion signaling pathways as well as defect in α-Actinin2-MLP protein interaction. Mice overexpressing the Zasp-1 isoform (no-LIM domain protein) develop cardiomyopathy, by altering the interaction between α-Actinin2 and ZASP-LIM domain protein and activate cardiac stress pathways associated with Hras, ERK and MAPK kinases.
Conclussion: Interaction between α-Actinin2 and LIM domain proteins is regulated by mechano-stretch signals. Defect in those interactions lead to cardiomyopathy by activation of stress signaling pathways.