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Phosphorylation of mycobacterial phosphodiesterase by eukaryotic-type Ser/Thr kinase controls its two distinct and mutually exclusive functionalities.

ABSTRACT: Phosphorylation-mediated negative feedback regulation of cAMP levels by phosphodiesterase is well-established in eukaryotic cells. However, such a mechanism remains unexplored in prokaryotes. We report here the involvement of eukaryotic-type Ser/Thr kinases, particularly PknA in trans-phosphorylating phosphodiesterase from Mycobacterium tuberculosis (mPDE), that resulted in decreased enzyme turnover rate compared with its unphosphorylated counterpart. To elucidate the role of mPDE phosphorylation in hydrolyzing cellular cAMP, we utilized a phosphodiesterase knock-out Escherichia coli strain, ?cpdA, where interference of endogenous eukaryotic-type Ser/Thr kinases could be excluded. Interestingly, the mPDE-complemented ?cpdA strain showed enhanced cAMP levels in the presence of PknA, and this effect was antagonized by PknA-K42N, a kinase-dead variant. Structural analysis of mPDE revealed that four Ser/Thr residues (Ser-20, Thr-22, Thr-182, and Thr-240) were close to the active site, indicating their possible role in phosphorylation-mediated alteration in enzymatic activity. Mutation of these residues one at a time to alanine or a combination of all four (mPDE-4A) affected catalytic activity of mPDE. Moreover, mPDE-4A protein in kinase assays exhibited reduction in its phosphorylation compared with mPDE. In consonance, phosphoproteins obtained after co-expression of PknA with mPDE/S20A/T240A/4A displayed decreased phospho-signal intensities in immunoblotting with anti-phosphoserine/phosphothreonine antibodies. Furthermore, unlike mPDE, phospho-ablated mPDE-T309A protein exhibited impaired cell wall localization in Mycobacterium smegmatis, whereas mPDE-4A behaved similarly as wild type. Taken together, our findings establish mutually exclusive dual functionality of mPDE upon PknA-mediated phosphorylation, where Ser-20/Thr-240 influence enzyme activity and Thr-309 endorses its cell wall localization.

SUBMITTER: Malhotra N

PROVIDER: S-EPMC5655513 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Phosphorylation of mycobacterial phosphodiesterase by eukaryotic-type Ser/Thr kinase controls its two distinct and mutually exclusive functionalities.

Malhotra Neha N Karthikeyan Subramanian S Chakraborti Pradip K PK

The Journal of biological chemistry 20170830 42

Phosphorylation-mediated negative feedback regulation of cAMP levels by phosphodiesterase is well-established in eukaryotic cells. However, such a mechanism remains unexplored in prokaryotes. We report here the involvement of eukaryotic-type Ser/Thr kinases, particularly PknA in trans-phosphorylating phosphodiesterase from <i>Mycobacterium tuberculosis</i> (mPDE), that resulted in decreased enzyme turnover rate compared with its unphosphorylated counterpart. To elucidate the role of mPDE phospho ...[more]

PMID: 28855253

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Project description:Cell growth and division require a balance between synthesis and hydrolysis of the peptidoglycan (PG). Inhibition of PG synthesis or uncontrolled PG hydrolysis can be lethal for the cells, making it imperative to control peptidoglycan hydrolase (PGH) activity. The synthesis or activity of several key enzymes along the PG biosynthetic pathway is controlled by the Hanks-type serine/threonine kinases (STKs). In Gram-positive bacteria, inactivation of genes encoding STKs is associated with a range of phenotypes, including cell division defects and changes in cell wall metabolism, but only a few kinase substrates and associated mechanisms have been identified. We previously demonstrated that STK-PrkC plays an important role in cell division, cell wall metabolism, and resistance to antimicrobial compounds in the human enteropathogen Clostridioides difficile In this work, we characterized a PG hydrolase, CwlA, which belongs to the NlpC/P60 family of endopeptidases and hydrolyses cross-linked PG between daughter cells to allow cell separation. We identified CwlA as the first PrkC substrate in C. difficile We demonstrated that PrkC-dependent phosphorylation inhibits CwlA export, thereby controlling hydrolytic activity in the cell wall. High levels of CwlA at the cell surface led to cell elongation, whereas low levels caused cell separation defects. Thus, we provided evidence that the STK signaling pathway regulates PGH homeostasis to precisely control PG hydrolysis during cell division.IMPORTANCE Bacterial cells are encased in a PG exoskeleton that helps to maintain cell shape and confers physical protection. To allow bacterial growth and cell separation, PG needs to be continuously remodeled by hydrolytic enzymes that cleave PG at critical sites. How these enzymes are regulated remains poorly understood. We identify a new PG hydrolase involved in cell division, CwlA, in the enteropathogen C. difficile Lack or accumulation of CwlA at the bacterial surface is responsible for a division defect, while its accumulation in the absence of PrkC also increases susceptibility to antimicrobial compounds targeting the cell wall. CwlA is a substrate of the kinase PrkC in C. difficile PrkC-dependent phosphorylation controls the export of CwlA, modulating its levels and, consequently, its activity in the cell wall. This work provides a novel regulatory mechanism by STK in tightly controlling protein export.

Dataset Information

Phosphorylation of mycobacterial phosphodiesterase by eukaryotic-type Ser/Thr kinase controls its two distinct and mutually exclusive functionalities.

Publications

Phosphorylation of mycobacterial phosphodiesterase by eukaryotic-type Ser/Thr kinase controls its two distinct and mutually exclusive functionalities.

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