Journal Article

<i>Mycoplasma hyorhinis</i> upregulates calpastatin and inhibits calpain-dependent proteolysis in SH-SY5Y neuroblastoma cells

Esther Elkind, Hagai Rechnitzer, Tali Vaisid, Jonathan D. Kornspan, Sivia Barnoy, Shlomo Rottem and Nechama S. Kosower

in FEMS Microbiology Letters

Volume 304, issue 1, pages 62-68
Published in print March 2010 |
Published online February 2010 | e-ISSN: 1574-6968 | DOI: https://dx.doi.org/10.1111/j.1574-6968.2009.01893.x

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Abstract

Mycoplasmas often contaminate cultured cells, leading to alterations in cellular gene expression, protein synthesis, signal transduction and metabolic pathways. Mycoplasmal contamination is often unnoticed, so that mycoplasma-induced alterations in cell functions may not be appreciated, unless specifically studied. Here, we show for the first time that contamination of SH-SY5Y cells by Mycoplasma hyorhinis leads to increased levels of calpastatin (the endogenous inhibitor of the Ca2+-dependent protease calpain), resulting in inhibition of Ca2+-induced calpain activation and inhibition of calpain-promoted proteolysis in the mycoplasmal-infected cells. Calpain activity is recovered upon calpastatin removal from extracts of contaminated cells. The calpain–calpastatin system has been implicated in a variety of physiological and pathological processes (signal transduction, motility, cell cycle, cell differentiation, membrane damage and apoptosis). Because the ratio of calpastatin to calpain is an important factor in the control of calpain activity within the cell, the elevated calpastatin may protect the mycoplasma-infected cells against certain types of damage (e.g. caused by high Ca2+). Thus, our results are important for studies on the modulation of host cells by mycoplasmas, and relevant to the pathobiology of processes involving mycoplasmal infections. The mycoplasma-infected cells provide a system for identifying factors that participate in the regulation of cellular calpastatin.

Keywords: mycoplasma–host cell interaction; calpain-promoted proteolysis; calpustatin; human cell cultures

Journal Article.  3971 words.  Illustrated.

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