The Eukaryote-Like Serine/Threonine Kinase STK Regulates the Growth and Metabolism of Zoonotic Streptococcus suis.

Chunyan Zhang,Meifang Tan,Wen Sun,Rui Zhou,Zhuofei Xu,Ting Gao,Lu Li,Mengmeng Dong,Wanquan Liu

doi:10.3389/fcimb.2017.00066

Abstract

Like eukaryotes, bacteria express one or more serine/threonine kinases (STKs) that initiate diverse signaling networks. The STK from Streptococcus suis is encoded by a single-copy stk gene, which is crucial in stress response and virulence. To further understand the regulatory mechanism of STK in S. suis, a stk deletion strain (Δstk) and its complementary strain (CΔstk) were constructed to systematically decode STK characteristics by applying whole transcriptome RNA sequencing (RNA-Seq) and phosphoproteomic analysis. Numerous genes were differentially expressed in Δstk compared with the wild-type parental strain SC-19, including 320 up-regulated and 219 down-regulated genes. Particularly, 32 virulence-associated genes (VAGs) were significantly down-regulated in Δstk. Seven metabolic pathways relevant to bacterial central metabolism and translation are significantly repressed in Δstk. Phosphoproteomic analysis further identified 12 phosphoproteins that exhibit differential phosphorylation in Δstk. These proteins are associated with cell growth and division, glycolysis, and translation. Consistently, phenotypic assays confirmed that the Δstk strain displayed deficient growth and attenuated pathogenicity. Thus, STK is a central regulator that plays an important role in cell growth and division, as well as S. suis metabolism.

Highlights

Upon sensing external stimuli, protein kinases, together with their cognate phosphatases, play a central role in signal transduction to quickly respond and adapt to constantly changing environments in both prokaryotes and eukaryotes
The STK in S. suis consists of a cytoplasmic kinase domain and an extracellular C-terminal region composed of four penicillinbinding proteins and a Ser/Thr kinase-associated domain (PASTA; residues 348–629 aa; Figure 1A; Beilharz et al, 2012)
Through “-omics” approaches, we found that S. suis STK can regulate expression of genes involved in bacterial central metabolism and virulence

Summary

Introduction

Protein kinases, together with their cognate phosphatases, play a central role in signal transduction to quickly respond and adapt to constantly changing environments in both prokaryotes and eukaryotes. Reversible phosphorylation occurs on specific amino acid residues, most commonly serine (Ser), threonine (Thr), tyrosine (Tyr), histidine (His), and aspartate (Asp) (Pereira et al, 2011). Kinases have been assumed to target only residues His and Asp, which are involved in two-component systems (TCS; Stock et al, 1990; Hoch, 2000). Increasing attention has been paid to the Ser/Thr kinases and their partner phosphatases. Ser/Thr kinases (eSTK)” (Pereira et al, 2011). Numerous bacterial eSTKs have been identified based on genome sequence databases (Galperin et al, 2010). Multiple eSTKs exist in most bacteria; comprehensively characterizing their essentiality and identifying their specific substrates are difficult. 11 eSTKs exist in Mycobacterium tuberculosis that has functional redundancy and/or substrate promiscuity (Boitel et al, 2003; Sajid et al, 2015)

Methods

Results

Discussion

Conclusion