Abstract-Extracellular matrix provides a structural, chemical, and mechanical substrate that is essential in cardiac development, growth, and responses to pathophysiological signals. Transmembrane receptors termed integrins provide a dynamic interaction of environmental cues and intracellular events. Integrins orchestrate multiple functions in the intact organism including organogenesis, regulation of gene expression, cell proliferation, differentiation, migration, and death. They are expressed in all cellular components of the cardiovascular system, including the vasculature, blood, cardiac myocytes and nonmuscle cardiac cells. The focus of this review will be on the role of integrins in the myocardium. We will provide background on integrin structure and function, discuss how the expression of integrins is critical to the form and function of the developing and postnatal myocardium, and review the known data on integrins as signaling molecules in the heart. Finally, we will offer insights to the future research directions into this important family of extracellular matrix receptors in the myocardium. Key Words: integrin â
ą myocardium â
ą extracellular matrix E xtracellular matrix (ECM) provides a structural, chemical, and mechanical substrate that is essential in cardiac development, growth, and responses to pathophysiological signals. Transmembrane receptors termed integrins provide a dynamic interaction of environmental cues and intracellular events. [1][2][3] Integrins orchestrate multiple functions in the intact organism including organogenesis, regulation of gene expression, cell proliferation, differentiation, migration, and death. They are expressed in all cellular components of the cardiovascular system, including the vasculature, blood, cardiac myocytes, and nonmuscle cardiac cells. The focus of this review will be on the role of integrins in the myocardium, because their function in the vasculature and platelets has been recently reviewed. 4,5 We will discuss how the expression of integrins is critical to the form and function of the myocardium, evaluate potential mechanisms of action of the integrins in the regulation of these processes, and offer insights to the future research directions into this important family of ECM receptors in the myocardium.
Integrin StructureIntegrins are noncovalently associated heterodimeric transmembrane receptors composed of ⣠and †subunits, with ⣠subunits ranging from 120 to 180 kDa whereas †subunits are 90 to 110 kDa. 3,6 Historically, integrins were identified based on an initial series of experiments suggesting a physical association between fibronectin and the intracellular cytoskeleton. 7 Subsequently, studies were published from several laboratories that (1) identified glycoproteins having characteristics of membrane proteins, and (2) showed that antibodies which recognized these proteins could inhibit cellular adhesion. 8 -12 These observations led to the cloning of chick fibroblast cDNAs that encoded for a molecule involved in transmembrane linkage between f...