Two communication bridges to one versatile molecule

Actin helical filaments are the key tools of the cytoskeleton for adapting cells to the physical or chemical microenvironment signals organizing cell contents, coordinating movement, or changing shape. Actin polymerization is controlled by regulatory proteins including nucleation, depolymerizing and severing factors, capping proteins, polymerases, crosslinkers, and stabilizing proteins. The cell's exquisite sensitivity in responding to a wide range of physical or chemical stimuli, is translated into cytoskeleton reorganization and adhesion-site modulation. Living cells survive, proliferate, or differentiate while they are anchored to their extracellular matrix. It comprises a complex bulk of information integrated into a coherent environmental signal. This is achieved through integrins that are the major family of transmembrane adhesion receptors composed of α and β units. These heterodimers not only play an anchorage mechanical role they also transmit chemical signals into the cell concerning their microenvironment and adhesive state. Integrin-based interaction networks follow an ordered series of events that range from their activation to focal adhesion assembly involving the participation of actin and actin binding proteins. Activated integrins link directly to the signalling and cytoskeletal systems regulating multiple cellular features, such as cell anchoring, locomotion, substrate deformation and matrix remodeling, in which actin possesses an essential role. Integration of incoming signals and whether to respond to these depends not only on integrin properties; an additional glycoprotein system named dystroglycan has demonstrated specific binding patterns to certain extracellular matrix components, supporting cell adhesion and translating signals. Dystroglycan was identified as Dystrophin glycoprotein complex (DGC) component; it comprises α- and β subunits. Alfa-dystroglycan is located at the extracellular peripheral membrane interacting with extracellular matrix proteins, while β-dystroglycan binds to α-dystroglycan on the extracellular face, and on its intracellular face to F-actin. Dystroglycan potential adhesion is due to its privileged position between cytoskeleton and extracellular matrix combined with their differential glycosylation patterns, tissue-specific expression, and multiple potential interactions. In this regard, dystroglycan has been found as a component of podosome adhesion structures, as well as in focal adhesions, interacting with vinexin, a vinculin binding partner. In this chapter, we focus on the relationship between the two specific transmembrane proteins that link the extracellular matrix and connect with F-actin to develop microenvironment-triggered responses, particularly regarding the focal adhesions, stress fibers, podosomes, and filopodia in which integrins and dystroglycans are involved.