Caveolae Dependent Endocytosis via Actin Stress Fiber

Recently, caveolae-mediated endocytosis has been implicated in the internalization of certain membrane components, extracellular ligands, bacterial toxins, and several nonenveloped viruses [42,43]. Simian virus 40 (SV40) utilizes endocytosis through caveolae to achieve infectious entry into host cells [44,45]. After binding to the caveolae, the virus particles induce the transient breakdown of actin stress fibers. Actin is then recruited to virus-loaded caveolae as actin patches are responsible sites for actin "tail" formation. Latrunculin A (an actin monomer-sequestering drug) and jasplakinolide (an actin polymer-stabilizing drug) both reduced virus internalization by 60-65% during the later stages of the entry process [46]. This result suggests that actin might function as a scaffold to restrict the lateral mobility of the caveolae. These events are dependent upon the presence of cholesterol and the activation of tyrosine kinases, which phosphorylate proteins in caveolae. SV40 particles induce tyrosine phosphorylation of proteins at virus-loaded caveolae, and thereby inhibition of tyrosine kinases inhibits the caveolae- mediated internalization of the virus. These findings indicate that the phosphorylation of caveolae proteins is essential for the formation of caveolae-derived endocytic vesicles and for viral infection into the cell [46]. Therefore, it is possible that tyrosine phosphorylation of caveolae-associated proteins might trigger the recruitment of components for F-actin assembly [46,47].

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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