Comparative Phenotypic, Proteomic, and Phosphoproteomic Analysis Reveals Different Roles of Serine/Threonine Phosphatase and Kinase in the Growth, Cell Division, and Pathogenicity of Streptococcus suis.

Qiao Hu,Lu Li,Qing-Gen Jiang,Xia Liao,Mei-Fang Tan,Hao-Tian Li,Roger R Draheim,Rui Zhou,Ting-Ting Li,Qi Huang,Lun Yao,Liang-Sheng Zhang

doi:10.3390/microorganisms9122442

Abstract

Eukaryote-like serine/threonine kinases (STKs) and cognate phosphatases (STPs) comprise an important regulatory system in many bacterial pathogens. The complexity of this regulatory system has not been fully understood due to the presence of multiple STKs/STPs in many bacteria and their multiple substrates involved in many different physiological and pathogenetic processes. Streptococci are the best materials for the study due to a single copy of the gene encoding STK and its cognate STP. Although several studies have been done to investigate the roles of STK and STP in zoonotic Streptococcus suis, respectively, few studies were performed on the coordinated regulatory roles of this system. In this study, we carried out a systemic study on STK/STP in S. suis by using a comparative phenotypic, proteomic, and phosphoproteomic analysis. Mouse infection assays revealed that STK played a much more important role in S. suis pathogenesis than STP. The ∆stk and ∆stp∆stk strains, but not ∆stp, showed severe growth retardation. Moreover, both ∆stp and ∆stk strains displayed defects in cell division, but they were abnormal in different ways. The comparative proteomics and phosphoproteomics revealed that deletion of stk or stp had a significant influence on protein expression. Interestingly, more virulence factors were found to be downregulated in ∆stk than ∆stp. In ∆stk strain, a substantial number of the proteins with a reduced phosphorylation level were involved in cell division, energy metabolism, and protein translation. However, only a few proteins showed increased phosphorylation in ∆stp, which also included some proteins related to cell division. Collectively, our results show that both STP and STK are critical regulatory proteins for S. suis and that STK seems to play more important roles in growth, cell division, and pathogenesis.

Highlights

Reversible protein phosphorylation is a key mechanism that regulates many cellular processes in both prokaryotes and eukaryotes [1]
As ∆stk showed retarded growth in Chemically defined minimal medium (CDM) but the growth was restored in CDM supplemented with multivitamins, by analyzing the differentially expressed genes in the mutants, we found that a coA-binding protein (NZ_CP020863.1_prot_WP_012027318.1_1268) was significantly downregulated in ∆stk but was not differentially expressed in ∆stp (Table S3)
Among the fourteen proteins that showed increased abundance after Ser/Thr phosphomodified peptide enrichment in the Δstp strain, only four proteins, including DivIVA, serine/threonine kinases (STKs), MltG, and GlmM, were involved in cell division, and the others were involved in metabolism, such as NADP, PrfA, GAPDH, OppF, Hprk, ArgS, SecA, and IDH (Table 2). These results suggested that STP and STK might affect the37cell division, energy metabolism, and protein translation of S.the suis∆stp in aand manner total of proteins were identified with changed abundance in both

Summary

Introduction

Reversible protein phosphorylation is a key mechanism that regulates many cellular processes in both prokaryotes and eukaryotes [1]. Protein phosphorylation, which is mainly mediated by histidine kinases (HKs), eukaryote-like serine/threonine. Microorganisms 2021, 9, 2442 kinases (STKs), and tyrosine kinases, plays an important role in a variety of biological processes [2,3,4,5]. Eukaryote-like serine/threonine kinases (STKs) and cognate phosphatases (STPs), as functional pairs [6,7], have emerged as important regulators with parallel or overlapping signaling networks for the regulation of many different physiological and pathogenetic processes in bacteria [3,8]. STK influences a wide range of physiological processes through its substrate proteins via modulating their phosphorylation states. The verified or suspected substrates of STK include DivIVA [24,25], MapZ [26], GpsB [27], FtsA, FtsZ [28], MacP [29], GlmM [7,30], and MurC [31]

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Discussion

Conclusion