The role of integrins in the development and homeostasis of the epidermis and skin appendages.

ABSTRACT Integrins play a critical role in the regulation of adhesion, migration, proliferation, and differentia-tion of cells. Because of the variety of the functions they play in the cell, they are necessary for the formation and maintenance of tissue structure integrity. The trove of data accumulated by researchers suggests that in-tegrins participate in the morphogenesis of the epidermis and its appendages. The development of mice with tissue-specific integrin genes knockout and determination of the genetic basis for a number of skin diseases in humans showed the significance of integrins in the biology, physiology, and morphogenesis of the epidermis and hair follicles. This review discusses the data on the role of different classes of integrin receptors in the biology of epidermal cells, as well as the development of the epidermis and hair follicles.KEyWORDS basement membrane; hair follicle; differentiation; integrins; keratinocytes; migration; morphogen-esis; proliferation; stem cells.ABBREVIATIONS BM – basement membrane; ECM – extracellular matrix; HF – hair follicle; SCs – stem cells; ESCs – embryonic stem cells; integrin-linked kinase (ILK).INTRODuCTIONIntegrins are the major class of surface receptors that attach to the extracellular matrix (ecM) and are re-sponsible for a cell’s interaction with its environment; these receptors process external signals into intracel-lular ones and induce a number of regulatory cascades. ultimately, this can lead to a variety of cellular re-sponses. Signals that come from intracellular receptors can regulate adhesion, migration, growth, differentia-tion, and death of cells. Integrin dysfunction in animals causes the development of various pathologies.Integrins are non-covalently attached heterodi-mer transmembrane receptors that consist of α- and β-subunits, forming a functional receptor. today, a to-tal of 18 α- and 8 β-subunits are known in vertebrates. these 26 subunits form at least 24 combinations of αβ receptors (Fig. 1). Integrins are divided into three classes depending on the type of β-subunit. β1 integrins form the most widespread group and usually bind to ecM proteins. β2 integrins are expressed in leucocytes only; some of them can bind to the surface proteins of other cells. Some β3 integrins are expressed in throm-bocytes and megakaryocytes and play a major role in the adhesion processes and blood clotting. Other β3 in-Fig. 1. Schematic representation of the heterodimeric integrin receptors family [1, 2]