Costameres, focal adhesions, and cardiomyocyte mechanotransduction

Abstract

Samarel, Allen M. Costameres, focal adhesions, and cardiomyocyte mechanotransduction. Am J Physiol Heart Circ Physiol 289: H2291-H2301, 2005; doi: 10.1152/ajpheart.00749.2005.-Mechanotransduction refers to the cellular mechanisms by which load-bearing cells sense physical forces, transduce the forces into biochemical signals, and generate appropriate responses leading to alterations in cellular structure and function. This process affects the beat-to-beat regulation of cardiac performance but also affects the proliferation, differentiation, growth, and survival of the cellular components that comprise the human myocardium. This review focuses on the experimental evidence indicating that the costamere and its structurally related structure the focal adhesion complex are critical cytoskeletal elements involved in cardiomyocyte mechanotransduction. Biochemical signals originating from the extracellular matrix-integrin-costameric protein complex share many common features with those signals generated by growth factor receptors. The roles of key regulatory kinases and other muscle-specific proteins involved in mechanotransduction and growth factor signaling are discussed, and issues requiring further study in this field are outlined.focal adhesion kinase; proline-rich tyrosine kinase 2; integrin-linked kinase; protein kinase C; signal transduction; heart THE PROCESS OF MECHANOTRANSDUCTION refers to the cellular mechanisms by which load-bearing cells sense physical forces, transduce the forces into biochemical signals, and generate appropriate responses leading to alterations in cellular structure and function. Physical forces encountered by living cells include membrane stretch, gain and loss of adhesion, and compression due to an increase in pressure. The signal transduction pathways that are activated in response to mechanical forces include many unique components, as well as elements shared by other signaling pathways. Mechanotransduction in cardiomyocytes is particularly complex, in that individual muscle cells both respond to externally applied mechanical forces as well as generate internal loads that are transmitted to adjacent cells and their surrounding extracellular matrix (ECM). Mechanotransduction in both atrial and ventricular cardiomyocytes affects the beat-to-beat regulation of cardiac performance but also profoundly affects the proliferation, differentiation, growth, and survival of the cellular components that comprise the human myocardium. Understanding the cellular and molecular basis for mechanotransduction is therefore important to our overall understanding of cardiac structure and function in the normal and diseased heart.Observational studies conducted during the 1970s addressing the hypertrophic growth response of human myocardium to pathological changes in systolic and diastolic wall stress (42) fostered the development of experimental model systems with which to explore cardiomyocyte mechanotransduction in vivo and in vitro. These model systems now span the breadth of experimental cardiology...

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“…In addition, it is clear that there are other types of matrix adhesions in addition to the FA, and furthermore, that there can be substantial variation in these structures when studied in 2D cultured cells vs. 3D systems more akin to that found in vivo in tissues/organs such as the heart. In CMs, integrins organize complexes concentrated adjacent to the sarcolemma that are analogous to the FA, known as costameres (9). Costameres are like the hoops of a barrel, providing stability for the cell.…”

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