Serratia marcescens ShlA hemolysin is inhibited by Ni2+

ELEONORA GARCÍA VÉSCOVI; MARTINA LAZZARO

Paraná

Congreso; LIV Reunión de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2019

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Serratia marcescens is an opportunistic human pathogen that represents a growing problem for public health. We have previously reported that S. marcescens is able to invade, survive and proliferate in non-phagocytic cells. After proliferation, the ShlAhemolysin is responsible for an increase in the cytosolic Ca2+ concentration, remodeling the actin cytoskeleton and promoting an exocytic-like egress. It has been reported that ShlA is necessary for cytotoxicity in different cells lines. At sub-lytic concentrations, it induces ATP depletion and K+ efflux. The aim of this work is to find tools that allow us to understand the function of ShlA. Performing invasion assays, co-localization with a calcium fluorophore and autophagy assays, we determined that in presence of Ni2+ wild-type Serratia behaves like a shlBA mutant. These assays were done in sub-lyticconditions and the phenotypes are blocked by the addition of the calcium chelator BAPTA-AM. Next, we performed hemolytic and cytotoxicity assays and we determined that the addition of Ni2+ to the wild-type strain prevented the lysis of the eukaryotic cells, obtaining a phenotype similar to the observed in the shlBA mutant. The addition of BAPTA-AM did not inhibit the eukaryotic cells lysis. We conclude that in presence of Ni2+ wild-type Serratia behaves like a shlBA mutant both in lytic and in non-lytic conditions. Moreover, we hypothesize that ShlA is responsible for two distinct phenotypes. The lytic phenotype is independent of the ShlA-mediated intracellular Ca2+ concentration fluctuations.In contrast, the ones that are induced in sub-lytic conditions of ShlA are dependent of a Ca2+ mobilization.