Contributor: Prof Alexander Bershadsky, MBI, Singapore Updated on: January 2012
Reviewer: Asst Prof Pakorn Tony Kanchanawong, MBI, Singapore
Reviewer: Asst Prof Pakorn Tony Kanchanawong, MBI, Singapore
Content
Major types of cell-matrix adhesions: 1) Focal adhesions (FAs) 2) Fibrillar adhesions (FBs) 3) Podosomes Steps in Formation
Additional Links
Common components of focal adhesions
Mechanisms of mechanosensing by FAs Factors affecting FA formation, dynamics and function Types of adhesion receptors: | Cell-Matrix Adhesions: Basic DescriptionCell-matrix interactions are mediated by adhesion receptors, leading to formation of multi-protein adhesion structures that interact with the actin cytoskeleton at the cell interior; they are collectively called cell-matrix adhesion complexes (CMACs) [1]. These adhesions act as vital information processing centers that enable cells to sense numerous extracellular signals that convey information about the chemistry, geometry, and physical properties of the ECM (reviewed in [2]). The substrate type or chemical composition (reviewed in [3]), its rigidity [4, 5], and the surface topography [6, 7, 8] (reviewed in [9, 10, 11]) influence force-induced events through CMACs, and mechanosensitive cells transmit this information through subsequent mechanotransduction pathways and signaling cascades to influence diverse processes such as the cell shape, polarity, fate, motility and deposition and/or restructuring of ECM components [4, 12, 13, 14] (reviewed in [2, 10, 15, 16]).Focal adhesions are the best-characterized among the different types of CMACs (links to the left) and are known to occur in different adhesion stages (as illustrated in the figure below) depending on the position and interplay of internal and external forces. FAs are known to evolve into fibrillar adhesions (FBs), which promote reorganization of the ECM while moving towards the center of the cell (reviewed in [17]). They are also capable of transforming into podosomes under certain conditions [18]. Such transitions could be of remarkable significance under physiological conditions. CMACs are highly dynamic and flexible, with their protein content ranging from a few components to over 100 different proteins (reviewed in [2, 19, 20]). They are assembled, disassembled, and translocated during cell spreading, polarization, migration, and division. The various types of CMACs not only differ in their basic features such as size, location, and shape, but they also differ in their composition, dynamics, component turnover and linkages to F-actin [21, 22]. It should be noted that:
 Figure: Types of cell-matrix adhesion complexes
Key Unanswered Questions
1. How do CMACs interact with cell-cell adhesions in order to coordinate the overall response to the cellular microenvironment?
2. Given the complexity and heterogeneity of the different CMACs, do they serve different functions, perhaps specific to cell types and matrix composition? 3. Do other integrins subtypes, beyond the classical α5β1 and αVβ3, have any functional significance in cell-matrix adhesions? 4. To what extent do other membrane proteins, that function as co-receptors, play a role? |
