JUN 16, 2015 12:11 PM PDT

Actin Right - and Left

WRITTEN BY: Ilene Schneider
Twisting protein fibers that form a cell's internal scaffolding called its cytoskeleton enable the cell to distinguish right from left, according to a study published in the April issue of Nature Cell Biology and reported by Tina Hesman Saey in Science News. The counterclockwise fibers, composed of actin, have such functions as helping cells to migrate from one part of a developing embryo to another, the article explained (https://www.sciencenews.org/article/twisty-chains-proteins-keep-cells-oriented).
A special assembly of protein in a cell helps the cell distinguish right from left and bind to other cells in order to move.
According to cell biologist Alexander Bershadsky and his colleagues, there is evidence that the cytoskeleton enables cells to distinguish right from left. Bershadsky is with the Mechanobiology Institute, National University of Singapore, and the Weizmann Institute of Science, Israel. He and his colleague, Yee Han Tee, videotaped actin fibers organizing inside of human foreskin cells that were placed under a microscope. They found that actin's natural asymmetry "leads fibers extending from the cell's edge to twist counterclockwise." Bershadsky explained that this orientation has an impact on navigation, mobility and other functions of the cell, "as if the direction of a screw's threads could determine how a whole machine works."

Bershadsky, who studies how cells move and how physical forces enable cells to attach themselves to the substrate and to one another, explained that actin is "the most abundant cellular protein in mammalian cells." Actin assembles into filaments. Along with hundreds of accessory proteins, including molecular motors of the myosin family, these filaments create various superstructures that together make up the actin cytoskeleton. The actin cytoskeleton has the functions of maintaining cell shape, generating cell motility, establishing cell adhesion to other cells and extracellular substrates and providing cell mechanosensitivity (http://labs.mbi.nus.edu.sg/abcd/index.html).

According to the Mechanobiology Institute at National University of Singapore, Bershadsky's studies were "among the first in which the phenomenon of adhesion-dependent mechanosensitivity was discovered and demonstrated." In these studies, Bershadsky and his colleagues demonstrated that focal adhesions function as extremely small mechanosensors, because the assembly of such adhesions depends on the use of external or cell-generated pulling forces. Bershadsky's current studies are attempting to clarify the mechanisms involved in the adhesion dependent mechanosensitivity. Some of his other studies involve the functions of microtubules in the regulation of cell motility and adhesion. His area of interest includes formins as potent regulators of actin assembly and actin-microtubule crosstalk (http://mbi.nus.edu.sg/alexander-bershadsky/).

"Actin self-organization in the cell is coordinated by diverse signaling molecules," Bershadsky concluded. "The main direction of our recent research focuses on understanding actin cytoskeleton- and adhesion-dependent mechanisms of cell mechanosensitivity and the establishment of left-right cell asymmetry."
About the Author
Ilene Schneider is the owner of Schneider the Writer, a firm that provides communications for health care, high technology and service enterprises. Her specialties include public relations, media relations, advertising, journalistic writing, editing, grant writing and corporate creativity consulting services. Prior to starting her own business in 1985, Ilene was editor of the Cleveland edition of TV Guide, associate editor of School Product News (Penton Publishing) and senior public relations representative at Beckman Instruments, Inc. She was profiled in a book, How to Open and Operate a Home-Based Writing Business and listed in Who's Who of American Women, Who's Who in Advertising and Who's Who in Media and Communications. She was the recipient of the Women in Communications, Inc. Clarion Award in advertising. A graduate of the University of Pennsylvania, Ilene and her family have lived in Irvine, California, since 1978.
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