Microfilaments: Actin Filaments (Campbell Biology)
Microfilaments are thin solid rods. They are also called actin filaments because they are built from molecules of actin, a globular protein. A microfilament is a twisted double chain of actin subunits. Besides occurring as linear filaments, microfilaments can form structural networks when certain proteins bind along the side of such a filament and allow a new filament to extend as a branch. Like microtubules, microfilaments seem to be present in all eukaryotic cells.
In contrast to the compression-resisting role of microtubules, the structural role of microfilaments in the cytoskeleton is to bear tension (pulling forces). A three-dimensional network formed by microfilaments just inside the plasma membrane (cortical microfilaments) helps support the cell’s shape. This network gives the outer cytoplasmic layer of a cell, called the cortex, the semisolid consistency of a gel, in contrast with the more fluid state of the interior cytoplasm. In some kinds of animal cells, such as nutrient-absorbing intestinal cells, bundles of microfilaments make up the core of microvilli, delicate projections that increase the cell’s surface area.
Microfilaments are well known for their role in cell motility. Thousands of actin filaments and thicker filaments made of a protein called myosin interact to cause contraction of muscle cells. In the unicellular eukaryote Amoeba and some of our white blood cells, localized contractions brought about by actin and myosin are involved in the amoeboid (crawling) movement of the cells. The cell crawls along a surface by extending cellular extensions called pseudopodia (from the Greek pseudes, false, and pod, foot) and moving toward them. In plant cells, actin-protein interactions contribute to cytoplasmic streaming, a circular flow of cytoplasm within cells. This movement, which is especially common in large plant cells, speeds the movement of organelles and the distribution of materials within the cell.
Urry, Lisa A.. Campbell Biology. Pearson Education. Kindle Edition. https://www.pearson.com/us/higher-education/series/Campbell-Biology-Series/2244849.html
Research Article: The Chromosomal Passenger Protein Birc5b Organizes Microfilaments and Germ Plasm in the Zebrafish Embryo
Date Published: April 18, 2013 Publisher: Public Library of Science Author(s): Sreelaja Nair, Florence Marlow, Elliott Abrams, Lee Kapp, Mary C. Mullins, Francisco Pelegri, Elizabeth R. Gavis Abstract: Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, astral microtubule-microfilament interactions also facilitate a stereotypic segregation pattern … Continue reading
Research Article: Actin Microfilament Mediates Osteoblast Cbfa1 Responsiveness to BMP2 under Simulated Microgravity
Date Published: May 10, 2013 Publisher: Public Library of Science Author(s): Zhongquan Dai, Feng Wu, Jian Chen, Hongjie Xu, Honghui Wang, Feima Guo, Yingjun Tan, Bai Ding, Jinfu Wang, Yumin Wan, Yinghui Li, Linda M. Hendershot. http://doi.org/10.1371/journal.pone.0063661 Abstract: Microgravity decreases osteoblastic activity, induces actin microfilament disruption and inhibits the responsiveness of osteoblast to cytokines, but the … Continue reading
Research Article: ROP GTPase-Dependent Actin Microfilaments Promote PIN1 Polarization by Localized Inhibition of Clathrin-Dependent Endocytosis
Date Published: April 3, 2012 Publisher: Public Library of Science Author(s): Shingo Nagawa, Tongda Xu, Deshu Lin, Pankaj Dhonukshe, Xingxing Zhang, Jiri Friml, Ben Scheres, Ying Fu, Zhenbiao Yang, Mark Estelle Abstract: A study in leaf epidermal pavement cells reveals that auxin activation of a Rho-like GTPase from plants induces inhibition of endocytosis through the … Continue reading
Date Published: September 23, 2009 Publisher: Public Library of Science Author(s): Araceli Castillo-Romero, Gloria Leon-Avila, Armando Perez Rangel, Rafael Cortes Zarate, Carlos Garcia Tovar, Jose Manuel Hernandez, Stefan Bereswill. http://doi.org/10.1371/journal.pone.0007156 Abstract: Microfilaments play a determinant role in different cell processes such as: motility, cell division, phagocytosis and intracellular transport; however, these structures are poorly understood in … Continue reading