Abstract
Efficient cell migration requires cellular polarization, which is characterized by the formation of leading and trailing edges, appropriate positioning of the nucleus and reorientation of the Golgi apparatus and centrosomes toward the leading edge. Migration also requires the development of an asymmetrical front-to-rear calcium (Ca2+) gradient to regulate focal adhesion assembly and actomyosin contractility. Here we demonstrate that silencing of syndecan-4, a transmembrane heparan sulfate proteoglycan, interferes with the correct polarization of migrating mammalian myoblasts (i.e., activated satellite stem cells). In particular, syndecan-4 knockdown completely abolished the intracellular Ca2+ gradient, abrogated centrosome reorientation and thus decreased cell motility, demonstrating the role of syndecan-4 in cell polarity. Additionally, syndecan-4 exhibited a polarized distribution during migration. Syndecan-4 knockdown cells exhibited decreases in the total movement distance during directional migration, maximum and vectorial distances from the starting point, as well as average and maximum cell speeds. Super-resolution direct stochastic optical reconstruction microscopy images of syndecan-4 knockdown cells revealed nanoscale changes in the actin cytoskeletal architecture, such as decreases in the numbers of branches and individual branch lengths in the lamellipodia of the migrating cells. Given the crucial importance of myoblast migration during embryonic development and postnatal muscle regeneration, we conclude that our results could facilitate an understanding of these processes and the general role of syndecan-4 during cell migration.
Highlights
Cell migration is a fundamentally important factor in various physiological and pathological processes, including morphogenesis, immune surveillance, tissue regeneration, and cancer cell metastasis (Ridley et al, 2003)
We evaluated the expression of syndecan-4 in C2C12 myoblasts transfected stably with plasmids expressing short hairpin RNAs (shRNAs) specific for syndecan-4 using Western blotting technique
As syndecan-4 silencing was shown to reduce myoblast migration, we studied the polarization of syndecan-4 knockdown cells using centrosome localization, an indicator of cell polarity in migrating cells (Etienne-Manneville and Hall, 2001; Zhang and Wang, 2017)
Summary
Cell migration is a fundamentally important factor in various physiological and pathological processes, including morphogenesis, immune surveillance, tissue regeneration, and cancer cell metastasis (Ridley et al, 2003). Cell motility and directed migration require the establishment of cell polarization, defined as the formation of distinct front and rear cellular areas This process is characterized by the emergence of an actin-mediated lamellipodial membrane protrusion, which. Cell motility is orchestrated by the formation of integrin-dependent adhesions to the surrounding matrix and the detachment of these adhesions from distinct regions at the rear of the cell (Lauffenburger and Horwitz, 1996; Ridley et al, 2003). These mechanisms direct the cell motility cycle and are required for cell migration in response to various factors. The mechanism by which this motility system integrates extracellular signals with cell polarity and cytoskeletal remodeling to promote directionally persistent migration remains unclear
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