Functional patterning of the developing myocardium by the non-canonical Wnt/L-Type Ca2+-channel pathway.

• Applicant: Professorin Dr. Daniela Panakova
• Subject Area: Anatomy and Physiology ; Cardiology, Angiology
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280799826

Ca2+ ions play key roles in cardiac biology, ranging from excitation-contraction coupling to the regulation of hormone secretion and gene expression. Voltage-dependent Ca2+ channels are crucial for Ca2+ handling in cardiac myocytes, and their impaired function contributes to the pathophysiology of the most common heart diseases, including arrhythmias or sudden cardiac death. In development, Ca2+ homeostasis is central to signaling pathways that control cell fate, differentiation, and organogenesis. We have recently shown that Wnt non-canonical signaling negatively regulates L-type Ca2+ channel (LTCC) conductance in the developing zebrafish heart. Failure to attenuate the Ca2+ influx via LTCC is detrimental for the emergence of intercellular electrical coupling gradients within the developing heart muscle and results in cardiac dysfunction. However, the exact molecular mechanisms of the interactions between Wnt non-canonical pathway and LTCC regulation are not yet fully characterized. Based on our preliminary results we hypothesize that the Wnt11 signaling may attenuate LTCC conductance by effecting its post-translational regulation rather than modulating the LTCC expression levels. Our data indicate that Wnt signaling might affect the Protein kinase A (PKA) pathway to attenuate LTCC function. In this proposal, we aim to define the molecular mechanisms by which Wnt non-canonical signaling regulates the LTCC function via PKA-dependent phosphorylation, and to identify the role of different LTCC C-termini in heart development and disease. To that end, we will use the H9c2 myoblast cell model to define the molecular bases of Wnt11 and LTCC interactions, and then test their physiologic relevance during heart development using zebrafish models that differentially express LTCC isoforms. Our work will expand the understanding of fundamental molecular mechanisms that lead to the proper formation of electrical intercellular coupling in the developing myocardium and their relevance in disease. Lastly, our work will allow us to elucidate the role of LTCCs in the pathophysiology of cardiac diseases as a basis for improved prevention, diagnosis, and treatment of arrhythmia.The specific aims are:1. Define how Wnt11 signaling attenuates the LTCC conductance.1.1 Analyze the effects of Wnt11 signaling on LTCC transcription and its alternative splicing.1.2 Study the proteolytic processing of LTCC in the absence of Wnt11 in early cardiogenesis.1.3 Characterize the cross-talk between Wnt11 and AKAP-PKA signaling in regulation of LTCC conductance.2. Analyze the role of distinct LTCC C-termini in cardiogenesis.2.1 Study the dynamics of LTCC C-termini localization in the absence of Wnt11.2.2 Determine the function of different LTCC C-termini in heart development.2.3 Analyze the role of protein interacting partners of distinct C-termini of LTCC in heart development and physiology.

• DFG Programme: Research Grants