Biology subjects

Santiviago, C. A.

Publications and source records attributed to Santiviago, C. A..

3 recordsLinked to original sources

bioRxiv2026

VopU is a novel T3SS effector protein with mono-ADP-ribosyltransferase activity and a non-canonical H-Y-Q catalytic triad

Vibrio parahaemolyticus utilizes its second Type III Secretion System (T3SS2) to deliver a suite of effector proteins that subvert eukaryotic host cell processes. In this study, we characterize VPA1312, renamed VopU, as a novel T3SS2 effector. We demonstrate that VopU is translocated into infected cells via the T3SS2 and independently of the VocC chaperone. From bioinformatic analyses, VopU is a member of a family of proteins distributed across diverse bacterial taxa and in some cases associated with T6SS gene clusters and plasmids. Sequence, structure-based, and functional analysis reveals that VopU harbors an ADP-ribosyltransferase domain with a non-canonical H-Y-Q catalytic triad, a motif not previously described in naturally occurring mono-ADP-ribosyltransferases. Heterologous expression of VopU within transfected cells or translocation of VopU during infection results in the ADP-ribosylation of a small protein of approximately 18 kDa protein distinct from the target of the previously described ADP-ribosyltransferase effector, VopT. While VopU is not essential for T3SS2-dependent cytotoxicity or intracellular survival of V. parahaemolyticus, heterologous expression of VopU induces host cell rounding and a transcriptional host stress response, likely linked to NAD depletion. These findings provide the initial characterization of this novel family of mono-ADP-ribosyltransferases and expand the known repertoire of bacterial effectors that mediate orthogonal post-translational modifications during host infection. IMPORTANCEVibrio parahaemolyticus is a leading cause of seafood-borne illness worldwide. To cause disease, the bacterium relies on a Type III Secretion System to deliver effector proteins into the cytosol of infected cells, subverting cellular processes. In this study, we identified a novel effector protein, VopU, which performs a post-translational modification known as ADP-ribosylation using a non-canonical catalytic triad (H-Y-Q). This is the first description of a naturally occurring mono-ART with this specific motif. We showed that VopU homologs are distributed across other bacterial species, and that VopU is active during infection of host cells. Together, our findings identify a novel family of effectors that can modify host proteins and potentially contribute to host colonization during infection.

microbiology↗

bioRxiv2023

Identification and distribution of novel candidate T6SS effectors encoded in Salmonella Pathogenicity Island 6

The type VI secretion system (T6SS) is a contact-dependent contractile multiprotein apparatus widely distributed in Gram-negative bacteria. These systems can deliver different effector proteins into target bacterial and/or eukaryotic cells, contributing to the environmental fitness and virulence of many bacterial pathogens. Salmonella harbors five different T6SSs encoded in different genomic islands. The T6SS encoded in Salmonella Pathogenicity Island 6 (SPI-6) contributes to Salmonella competition with the host microbiota and its interaction with infected host cells. Despite its relevance, information regarding the total number of effector proteins encoded within SPI-6 and its distribution among different Salmonella enterica serotypes is limited. In this work, we performed bioinformatic and comparative genomics analyses of the SPI-6 T6SS gene cluster to expand our knowledge regarding the T6SS effector repertoire and the global distribution of these effectors in Salmonella. The analysis of a curated dataset of 60 Salmonella enterica genomes from the Secret6 database revealed the presence of 23 novel putative T6SS effector/immunity protein (E/I) modules. These effectors were concentrated in the variable regions 1 to 3 (VR1-3) of the SPI-6 T6SS gene cluster. VR1-2 were enriched in candidate effectors with predicted peptidoglycan hydrolase activity, while VR3 was enriched in candidate effectors of the Rhs family with C-terminal extensions with predicted DNase, RNase, deaminase, or ADP-ribosyltransferase activity. A global analysis of known and candidate effector proteins in Salmonella enterica genomes from the NCBI database revealed that T6SS effector proteins are differentially distributed among Salmonella serotypes. While some effectors are present in over 200 serotypes, others are found in less than a dozen. A hierarchical clustering analysis identified Salmonella serotypes with distinct profiles of T6SS effectors and candidate effectors, highlighting the diversity of T6SS effector repertoires in Salmonella enterica. The existence of different repertoires of effector proteins suggests that different effector protein combinations may have a differential impact on the environmental fitness and pathogenic potential of these strains.

microbiology↗

bioRxiv2019

SopB- and SifA-dependent shaping of the Salmonella-containing vacuole proteome in the social amoeba Dictyosteliumdiscoideum

The ability of Salmonella to survive and replicate within mammalian host cells involves the generation of a membranous compartment known as the Salmonella-containing vacuole (SCV). Salmonella employs a number of effector proteins that are injected into host cells for SCV formation using its type-three secretion systems encoded in SPI-1 and SPI-2 (T3SSSPI-1 and T3SSSPI-2, respectively). Recently, we reported that S. Typhimurium requires T3SSSPI-1 and T3SSSPI-2 to survive in the model amoeba Dictyostelium discoideum. Despite these findings, the involved effector proteins have not been identified yet. Therefore, we evaluated the role of two major S. Typhimurium effectors SopB and SifA during D. discoideum intracellular niche formation. First, we established that S. Typhimurium resides in a vacuolar compartment within D. discoideum. Next, we isolated SCVs from amoebae infected with wild type or the {Delta}sopB and {Delta}sifA mutant strains of S. Typhimurium, and we characterized the composition of this compartment by quantitative proteomics. This comparative analysis suggests that S. Typhimurium requires SopB and SifA to modify the SCV proteome in order to generate a suitable intracellular niche in D. discoideum. Accordingly, we observed that SopB and SifA are needed for intracellular survival of S. Typhimurium in this organism. Thus, our results provide insight into the mechanisms employed by Salmonella to survive intracellularly in phagocytic amoebae. ImportanceThe molecular mechanisms involved in Salmonella survival to predation by phagocytic amoebae, such as D. discoideum, remains poorly understood. Although we established that S. Typhimurium requires two specialized type-three secretion systems to survive in D. discoideum, no effector protein has been implicated in this process so far. Here, we confirmed the presence of a membrane-bound compartment containing S. Typhimurium in D. discoideum, and purified the D. discoideum SCV to characterize the associated proteome. In doing so, we established a key role for effector proteins SopB and SifA in remodeling the protein content of the SCV that ultimately allow the intracellular survival of S. Typhimurium in D. discoideum. We also discuss similarities and differences with the proteomes of the human SCV. These findings contribute to unravel the mechanisms used by Salmonella to survive in the environment exploiting phagocytic amoebae as a reservoir.

microbiology↗