Biophysical characterization of actin bundles generated by the Chlamydia trachomatis Tarp effector

Chlamydia trachomatis entry into host cells is mediated by pathogen-directed remodeling of the actin cytoskeleton. The chlamydial type III secreted effector, translocated actin recruiting phosphoprotein (Tarp), has been implicated in the recruitment of actin to the site of internalization. Tarp harb...

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Bibliographic Details
Published in:	Biochemical and biophysical research communications 2018-06, Vol.500 (2), p.423-428
Main Authors:	Ghosh, Susmita, Park, Jinho, Thomas, Mitchell, Cruz, Edgar, Cardona, Omar, Kang, Hyeran, Jewett, Travis
Format:	Article
Language:	eng
Subjects:	60 APPLIED LIFE SCIENCES ACTIN Actin bundles Actins - metabolism ANIMAL CELLS Bending persistence length Biophysical Phenomena Chlamydia trachomatis Chlamydia trachomatis - metabolism Cytoskeleton Effector Fluorescence MICROTUBULES PHOSPHOPROTEINS Phosphoproteins - chemistry Phosphoproteins - metabolism PROLINE Protein Domains Tarp
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Summary:	Chlamydia trachomatis entry into host cells is mediated by pathogen-directed remodeling of the actin cytoskeleton. The chlamydial type III secreted effector, translocated actin recruiting phosphoprotein (Tarp), has been implicated in the recruitment of actin to the site of internalization. Tarp harbors G-actin binding and proline rich domains required for Tarp-mediated actin nucleation as well as unique F-actin binding domains implicated in the formation of actin bundles. Little is known about the mechanical properties of actin bundles generated by Tarp or the mechanism by which Tarp mediates actin bundle formation. In order to characterize the actin bundles and elucidate the role of different Tarp domains in the bundling process, purified Tarp effectors and Tarp truncation mutants were analyzed using Total Internal Reflection Fluorescence (TIRF) microscopy. Our data indicate that Tarp mediated actin bundling is independent of actin nucleation and the F-actin binding domains are sufficient to bundle actin filaments. Additionally, Tarp-mediated actin bundles demonstrate distinct bending stiffness compared to those crosslinked by the well characterized actin bundling proteins fascin and alpha-actinin, suggesting Tarp may employ a novel actin bundling strategy. The capacity of the Tarp effector to generate novel actin bundles likely contributes to chlamydia's efficient mechanism of entry into human cells. •The F-actin binding domain of Tarp is sufficient to bundle filamentous actin.•Actin bundles formed by Tarp are more flexible than that of α-actinin and fascin.•Tarp mediated actin bundling is independent of actin nucleation.
ISSN:	0006-291X 1090-2104