Extracellular Matrix of Animal Cells (Campbell Biology)
Although animal cells lack walls akin to those of plant cells, they do have an elaborate extracellular matrix (ECM). The main ingredients of the ECM are glycoproteins and other carbohydrate-containing molecules secreted by the cells. (Recall that glycoproteins are proteins with covalently bonded carbohydrates, usually short chains of sugars.) The most abundant glycoprotein in the ECM of most animal cells is collagen, which forms strong fibers outside the cells. In fact, collagen accounts for about 40% of the total protein in the human body. The collagen fibers are embedded in a network woven out of proteoglycans secreted by cells. A proteoglycan molecule consists of a small core protein with many carbohydrate chains covalently attached, so that it may be up to 95% carbohydrate. Large proteoglycan complexes can form when hundreds of proteoglycan molecules become noncovalently attached to a single long polysaccharide molecule. Some cells are attached to the ECM by ECM glycoproteins such as fibronectin. Fibronectin and other ECM proteins bind to cell-surface receptor proteins called integrins that are built into the plasma membrane. Integrins span the membrane and bind on their cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. The name integrin is based on the word integrate: Integrins are in a position to transmit signals between the ECM and the cytoskeleton and thus to integrate changes occurring outside and inside the cell.
Current research on fibronectin, other ECM molecules, and integrins reveals the influential role of the ECM in the lives of cells. By communicating with a cell through integrins, the ECM can regulate a cell’s behavior. For example, some cells in a developing embryo migrate along specific pathways by matching the orientation of their microfilaments to the “grain” of fibers in the extracellular matrix. Researchers have also learned that the extracellular matrix around a cell can influence the activity of genes in the nucleus. Information about the ECM probably reaches the nucleus by a combination of mechanical and chemical signaling pathways. Mechanical signaling involves fibronectin, integrins, and microfilaments of the cytoskeleton. Changes in the cytoskeleton may in turn trigger signaling pathways inside the cell, leading to changes in the set of proteins being made by the cell and therefore changes in the cell’s function. In this way, the extracellular matrix of a particular tissue may help coordinate the behavior of all the cells of that tissue. Direct connections between cells also function in this coordination.
Urry, Lisa A.. Campbell Biology. Pearson Education. Kindle Edition. https://www.pearson.com/us/higher-education/series/Campbell-Biology-Series/2244849.html
Research Article: Fibronectin Deposition Participates in Extracellular Matrix Assembly and Vascular Morphogenesis
Date Published: January 26, 2016 Publisher: Public Library of Science Author(s): Abigail Hielscher, Kim Ellis, Connie Qiu, Josh Porterfield, Sharon Gerecht, Donald Gullberg. http://doi.org/10.1371/journal.pone.0147600 Abstract: The extracellular matrix (ECM) has been demonstrated to facilitate angiogenesis. In particular, fibronectin has been documented to activate endothelial cells, resulting in their transition from a quiescent state to an … Continue reading
Date Published: October 22, 2018 Publisher: Public Library of Science Author(s): C. Mendoza-Topaz, G. Nelson, G. Howard, S. Hafner, P. Rademacher, M. Frick, B. J. Nichols, Ivan R Nabi. http://doi.org/10.1371/journal.pone.0205306 Abstract: A range of cellular functions have been attributed to caveolae, flask-like invaginations of the plasma membrane. Here, we have used RNA-seq to achieve quantitative … Continue reading
Date Published: July 18, 2018 Publisher: Public Library of Science Author(s): Rabab Sharif, Ben Fowler, Dimitrios Karamichos, Rajiv R. Mohan. http://doi.org/10.1371/journal.pone.0200704 Abstract: Keratoconus (KC) is a common multifactorial ectatic corneal disease with unknown onset. KC most commonly appears in adolescence and affects approximately 1:400 people worldwide. Treatment options, for advanced KC cases, are collagen cross-linking … Continue reading
Date Published: February 2, 2017 Publisher: Public Library of Science Author(s): Jinglei Wu, Priya Ravikumar, Kytai T. Nguyen, Connie C. W. Hsia, Yi Hong, Xiaoming He. http://doi.org/10.1371/journal.pone.0171165 Abstract: Decellularized extracellular matrix (ECM) contains complex tissue-specific components that work in concert to promote tissue repair and constructive remodeling and has been used experimentally and clinically to … Continue reading
Date Published: March 21, 2016 Publisher: Public Library of Science Author(s): Andrea Baiocchini, Claudia Montaldo, Alice Conigliaro, Alessio Grimaldi, Virginia Correani, Francesco Mura, Fabiola Ciccosanti, Nicolina Rotiroti, Alessia Brenna, Marzia Montalbano, Gianpiero D’Offizi, Maria Rosaria Capobianchi, Riccardo Alessandro, Mauro Piacentini, Maria Eugenia Schininà, Bruno Maras, Franca Del Nonno, Marco Tripodi, Carmine Mancone, Matias A Avila. … Continue reading