The ShcA Phosphotyrosine Docking Protein Uses Distinct Mechanisms to Regulate Myocyte and Global Heart Function

Abstract

Rationale Although tyrosine kinases (TKs) are important for cardiac function, their relevant downstream targets in the adult heart are unknown. The ShcA docking protein binds specific phosphotyrosine (pTyr) sites on activated TKs through its N-terminal pTyr-binding (PTB) and C-terminal SH2 domains and stimulates downstream pathways through motifs such as pTyr sites in its central CH1 region. Therefore, ShcA could be a potential hub for downstream TK signaling in the myocardium. Objective To define the role of ShcA, a TK scaffold, in the adult heart using a myocardial-specific knockout of murine ShcA (ShcA CKO) and domain knock-in models. Methods and Results ShcA CKO mice developed a dilated cardiomyopathy phenotype involving impaired systolic function with enhanced cardiomyocyte contractility. This uncoupling of global heart and intrinsic myocyte functions was associated with altered collagen and extracellular matrix compliance properties, suggesting disruption of mechanical coupling. In vivo dissection of ShcA signaling properties revealed that selective inactivation of the PTB domain in the myocardium had effects resembling those seen in ShcA CKO mice, whereas disruption of the SH2 domain caused a less severe cardiac phenotype. Downstream signaling through the CH1 pTyr sites was dispensable for baseline cardiac function but necessary to prevent adverse remodeling after hemodynamic overload. Conclusions These data demonstrate a requirement for TK-ShcA PTB domain signaling to maintain cardiac function. In addition, analysis of the SH2 domain and CH1 pTyr sites reveals that ShcA mediates pTyr signaling in the adult heart through multiple distinct signaling elements that control myocardial functions and response to stresses.

p66Shc Couples Mechanical Signals to RhoA through Focal Adhesion Kinase-Dependent Recruitment of p115-RhoGEF and GEF-H1

“…Application of shear stress to endothelial cells, for instance, induces the association of all three Shc isoforms with ␤ 1 and ␣ v ␤ 3 integrins, and abnormal shear patterns in mouse vasculature stimulate Shc translocation to junctional mechanosensory complexes (34,35). Conditional deletion of all Shc isoforms in cardiomyocytes leads to impaired mechanical coupling, and knock-in mutants of Shc prevent the formation of muscle spindles, mechanosensory organs within skeletal muscle (36,37). In this study, we link Shc with tension-induced RhoA activity, providing a potential mechanism for such observations and for multiple cellular processes related to RhoAlinked force transduction.…”

The adaptor protein Shc integrates growth factor and ECM signaling during postnatal angiogenesis

“…More detailed gene-targeting work has shown that the expression of the PTB domain of Shc specifically in cardiomyocytes is critical for midgestational heart development and embryonic life. 11 Conditional knockout strategies have shown that Shc is also important for the proper development/function of other organs such as skeletal muscle, 11 brain, 12 cardiomyocytes, 13 and thymocytes, 14 because tissue-specific deletion of Shc resulted in living but underdeveloped mice. To address the role of Shc in angiogenesis in vivo, we studied loss of Shc function using morpholino (MO) antisense technology in zebrafish.…”

The Src Homology and Collagen A (ShcA) Adaptor Protein Is Required for the Spatial Organization of the Costamere/Z-disk Network during Heart Development

“…These events lead to the activation of the Erk/mitogen-activated protein kinase pathway and cell proliferation (5,8). Germline deletion of ShcA in mice leads to profound embryonic cardiovascular defects (9), whereas deletion of ShcA in cardiomyocytes after birth induces a moderately impaired systolic function (10). Thus, ShcA plays a crucial role during heart development, but the underlying molecular mechanisms are largely unknown.…”