HilD and PhoP independently regulate the expression of grhD1, a novel gene required for Salmonella Typhimurium invasion of host cells

Banda, María M.; López, Carmen; Manzo, Rubiceli; Rico-Pérez, Gadea; García, Pablo D.; Rosales-Reyes, Roberto; Cruz, Miguel A. De la; Soncini, Fernando C.; Portillo, Francisco García-delÂ; Bustamante, Vı́ctor H.

doi:10.1038/s41598-018-23068-0

Cited by 10 publications

(14 citation statements)

References 91 publications

(127 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Likewise, HilD induces expression of the SPI-2 genes, which are mainly required for replication of Salmonella within host cells, by acting on the ssrAB operon that codes for the SsrA/SsrB two-component system, the master regulator of SPI-2 25,36,37 . Additionally, HilD directly controls expression of several other virulence genes 28,38–40 . For all cases characterized up to now, HilD induces expression of target genes by directly antagonizing repression mediated by the histone-like protein H-NS on the respective promoters 36,37,41–43 .…”

Section: Introductionmentioning

confidence: 99%

HilD induces expression of a novel Salmonella Typhimurium invasion factor, YobH, through a regulatory cascade involving SprB

Banda

Manzo

Bustamante

2019

Sci Rep

Self Cite

View full text Add to dashboard Cite

HilD is an Arac-like transcriptional regulator encoded in the Salmonella pathogenicity island 1 (SPI-1), which actives transcription of many genes within and outside SPI-1 that are mainly required for invasion of Salmonella into host cells. HilD controls expression of target genes directly or by acting through distinct regulators; three different regulatory cascades headed by HilD have been described to date. Here, by analyzing the effect of HilD on the yobH gene in Salmonella enterica serovar typhimurium (S. Typhimurium), we further define an additional regulatory cascade mediated by HilD, which was revealed by previous genome-wide analyses. in this regulatory cascade, HilD acts through SprB, a LuxR-like regulator encoded in SPI-1, to induce expression of virulence genes. Our data show that HilD induces expression of sprB by directly counteracting H-nS-mediated repression on the promoter region upstream of this gene. then, SprB directly activates expression of several genes including yobH, slrP and ugtL. Interestingly, we found that YobH, a protein of only 79 amino acids, is required for invasion of S. typhimurium into HeLa cells and mouse macrophages. thus, our results reveal a novel S. typhimurium invasion factor and provide more evidence supporting the HilD-SprB regulatory cascade.The genus Salmonella groups facultative anaerobic Gram-negative bacteria and is divided into two species, S. enterica and S. bongori. The former is responsible for diseases ranging from gastroenteritis to severe systemic infections in a wide range of hosts, and it comprises 6 subspecies that are further divided into serovars 1,2 . The broad-host-range S. enterica serovar Typhimurium (S. Typhimurium) is a common cause of gastroenteritis in humans and many animals worldwide; furthermore, it can also cause systemic infection in humans and some animals, including laboratory mice 1,3,4 . For this reason, S. Typhimurium is frequently used as a model for studying the host-pathogen interactions during infection with Salmonella.

show abstract

Section: Introductionmentioning

confidence: 99%

HilD induces expression of a novel Salmonella Typhimurium invasion factor, YobH, through a regulatory cascade involving SprB

Banda

Manzo

Bustamante

2019

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…Either deletion of phoPQ or introduction of a constitutive phoQ allele (phoQ24) leads to a similarly massive virulence defect that increases the median lethal dose by approximately 5 orders of magnitude in BALB/c mice (2,29,33), suggesting that regulation of the system is essential. PhoP controls a large regulon, including the Salmonella pathogenicity island 2 (SPI2) T3SS, and additional genes that contribute to survival within the macrophage (28,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43). When activated, the PhoPQ system has also been shown to repress transcription of hilA, encoding the main SPI1 T3SS activator (44,45), but how PhoPQ represses SPI1 is unclear.…”

mentioning

confidence: 99%

PhoP-Mediated Repression of the SPI1 Type 3 Secretion System in Salmonella enterica Serovar Typhimurium

2019

View full text Add to dashboard Cite

Salmonella must rapidly adapt to various niches in the host during infection. Relevant virulence factors must be appropriately induced, and systems that are detrimental in a particular environment must be turned off. Salmonella infects intestinal epithelial cells using a type 3 secretion system (T3SS) encoded on Salmonella pathogenicity island 1 (SPI1). The system is controlled by three AraC-like regulators, HilD, HilC, and RtsA, which form a complex feed-forward loop to activate expression of hilA, encoding the main transcriptional regulator of T3SS structural genes. This system is tightly regulated, with many of the activating signals acting at the level of hilD translation or HilD protein activity. Once inside the phagosomes of epithelial cells, or in macrophages during systemic stages of disease, the SPI1 T3SS is no longer required or expressed. Here, we show that the PhoPQ two-component system, critical for intracellular survival, appears to be the primary mechanism by which Salmonella shuts down the SPI1 T3SS. PhoP negatively regulates hilA through multiple distinct mechanisms: direct transcriptional repression of the hilA promoter, indirect transcriptional repression of both the hilD and rtsA promoters, and activation of the small RNA (sRNA) PinT. Genetic analyses and electrophoretic mobility shift assays suggest that PhoP specifically binds the hilA promoter to block binding of activators HilD, HilC, and RtsA as a mechanism of repression. IMPORTANCE Salmonella is one of the most common foodborne pathogens, causing an estimated 1.2 million illnesses per year in the United States. A key step in infection is the activation of the bacterial invasion machinery, which induces uptake of the bacterium into epithelial cells and leads to induction of inflammatory diarrhea. Upon entering the vacuolar compartments of host cells, Salmonella senses an environmental transition and represses the invasion machinery with a two-component system relevant for survival within the vacuole. This adaptation to specific host niches is an important example of how signals are integrated for survival of the pathogen.

show abstract

“…Accordingly, the slyA gene is expressed during growth in rich and minimal media (17,36,67,68). Furthermore, SlyA is required for the expression of the grhD1 virulence gene in both LB and N-MM (44). Our results show that SlyA induces the expression of ssrAB during growth in LB by counteracting H-NS-mediated repression.…”

Section: Discussionmentioning

confidence: 67%

“…acts as a dominant negative mutant (61). In this way, the expression of the ssrAB-catϪ302/ϩ478 fusion was assessed in the WT S. Typhimurium strain and its derivative ΔslyA mutant containing the empty vector pMPM-T6⍀, or the pT6-HNS-WT or pT6-HNS-G113D plasmids, which express WT H-NS and the H-NS G113D mutant, respectively, from an arabinose-inducible promoter (44,61). The strains were grown in LB at 37°C in the presence or absence of 0.1% arabinose to induce or not induce the expression of the H-NS proteins.…”

Section: Slya Counteracts Repression Exerted By H-ns On Ssrab During mentioning

confidence: 99%

“…5 and 6, the expression of these fusions was not affected in the ΔssrB and ΔphoP mutants with respect to the WT strain. As controls for these assays, the expression of the ssaG-cat and pagK-cat transcriptional fusions, which is dependent on SsrB (62) and PhoP (44), respectively, was also analyzed in the respective ΔssrB or ΔphoP mutant. As expected, the expression of ssaG-cat and pagK-cat decreased specifically by the absence of SsrB or PhoP, respectively, in both LB and N-MM ( Fig.…”

Section: Slya and Hild Additively Antagonize Repression Of H-ns On Ssmentioning

confidence: 99%

See 1 more Smart Citation

SlyA and HilD Counteract H-NS-Mediated Repression on the ssrAB Virulence Operon of Salmonella enterica Serovar Typhimurium and Thus Promote Its Activation by OmpR

et al. 2019

Self Cite

View full text Add to dashboard Cite

H-NS-mediated repression of acquired genes and the subsequent adaptation of regulatory mechanisms that counteract this repression have played a central role in the Salmonella pathogenicity evolution. The Salmonella pathogenicity island 2 (SPI-2) is an acquired chromosomal region containing genes necessary for Salmonella enterica to colonize and replicate in different niches of hosts. The ssrAB operon, located in SPI-2, encodes the two-component system SsrA-SsrB, which positively controls the expression of the SPI-2 genes but also other many genes located outside SPI-2. Several regulators have been involved in the expression of ssrAB, such as the ancestral regulators SlyA and OmpR, and the acquired regulator HilD. In this study, we show how SlyA, HilD, and OmpR coordinate to induce the expression of ssrAB under different growth conditions. We found that when Salmonella enterica serovar Typhimurium is grown in nutrient-rich lysogeny broth (LB), SlyA and HilD additively counteract H-NS-mediated repression on ssrAB, whereas in N-minimal medium (N-MM), SlyA antagonizes H-NS-mediated repression on ssrAB independently of HilD. Interestingly, our results indicate that OmpR is required for the expression of ssrAB independently of the growth conditions, even in the absence of repression by H-NS. Therefore, our data support two mechanisms adapted for the expression of ssrAB under different growth conditions. One involves the additive action of SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on ssrAB, thus favoring in both cases the activation of ssrAB by OmpR. IMPORTANCE The global regulator H-NS represses the expression of acquired genes and thus avoids possible detrimental effects on bacterial fitness. Regulatory mechanisms are adapted to induce expression of the acquired genes in particular niches to obtain a benefit from the information encoded in the foreign DNA, as for pathogenesis. Here, we show two mechanisms that were integrated for the expression of virulence genes in Salmonella Typhimurium. One involves the additive action of the regulators SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on the ssrAB operon, thus favoring its activation by the OmpR regulator. To our knowledge, this is the first report involving the coordinated action of two regulators to counteract H-NS-mediated repression.

show abstract

HilD and PhoP independently regulate the expression of grhD1, a novel gene required for Salmonella Typhimurium invasion of host cells

Cited by 10 publications

References 91 publications

HilD induces expression of a novel Salmonella Typhimurium invasion factor, YobH, through a regulatory cascade involving SprB

HilD induces expression of a novel Salmonella Typhimurium invasion factor, YobH, through a regulatory cascade involving SprB

PhoP-Mediated Repression of the SPI1 Type 3 Secretion System in Salmonella enterica Serovar Typhimurium

SlyA and HilD Counteract H-NS-Mediated Repression on the ssrAB Virulence Operon of Salmonella enterica Serovar Typhimurium and Thus Promote Its Activation by OmpR

Contact Info

Product

Resources

About