Features | Partner Sites | Information | LinkXpress
Sign In
PURITAN MEDICAL
GLOBETECH PUBLISHING LLC
GLOBETECH PUBLISHING LLC

Bacterial Persistence to Antibiotic Treatment Mediated by HipA Toxin Inhibition of Glutamyl-tRNA-Synthetase Activity

By BiotechDaily International staff writers
Posted on 06 Jan 2014
A team of molecular microbiologists has identified the molecular pathway that induces some types of "persistent" bacteria to enter a static or dormant phase when faced with antibiotic treatment.

Bacterial persistence or multidrug tolerance is caused by a small subpopulation of microbial cells termed persisters. Persisters, which are the main cause for relapsing and chronic infections, are not mutants, but rather are dormant cells that can survive the antimicrobial treatments that kill the majority of their genetically identical siblings. Persister cells have entered a non- or extremely slow-growing physiological state, which makes them insensitive to the action of antimicrobial drugs. When such persisting microbial cells cannot be eliminated by the immune system, they become a reservoir from which recurrence of infection will develop.

In a recent study investigators at the Hebrew University of Jerusalem (Israel) searched for a molecular explanation for bacterial persistence by screening an expression library for putative targets of HipA, the first toxin linked to persistence. HipA belongs to a family of phosphatidylinositide and protein kinases and is capable of autophosphorylation. It causes inhibition of macromolecular synthesis, but the mechanism of action is unknown. Mutants of HipA lacking either predicted active-site residues or the site of autophosphorylation are defective in producing multidrug-tolerant cells.

The investigators reported in the December 17, 2013, online edition of the journal Nature Communications that GltX, the glutamyl-tRNA-synthetase, reversed the toxicity of HipA and prevented the development of persistent forms. GltX is a member of the enzyme family that catalyzes the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction.

Upon HipA expression, GltX activity was blocked, as the enzyme was phosphorylated at Ser239 (amino acid serine residue 239), its ATP-binding site. This phosphorylation led to accumulation of uncharged tRNA(Glu) in the cell, which resulted in the activation of the stringent response. The stringent response is a stress response of bacteria and plant chloroplasts in reaction to amino-acid starvation, fatty acid limitation, iron limitation, heat shock, and other stress conditions. The stringent response modulates transcription of up to one-third of all genes in the cell. This in turn causes the cell to divert resources away from growth and division and toward amino acid synthesis in order to promote survival until nutrient conditions improve.

The investigators stated that, "Our findings demonstrate a mechanism for persister formation by the hipBA toxin-antitoxin module and provide an explanation for the long-observed connection between persistence and the stringent response."

Related Links:

Hebrew University of Jerusalem



Channels

Drug Discovery

view channel
Image: Scanning electron microscope (SEM) image of a field of polypyrrole nanowires (Photo courtesy of Dr. Richard Borgens, Purdue University).

Novel Controlled-Release Drug Delivery System Heals Spinal Inflammation in Mouse Model

A novel drug delivery system that allows controllable release of an anti-inflammatory agent directly to the site of inflammation or injury was tested successfully in a mouse model. Investigators at... Read more

Business

view channel

Biopharm Startup to Commercialize Antibody Therapy for Drug Resistant Cancers

A biopharm startup company has licensed the rights to commercialize an antibody-based approach for treatment of drug resistant cancers. The new company, CadheRx Therapeutics (La Jolla, CA, USA), entered into a licensing agreement with Stony Brook University (NY, USA) to develop and market an anticancer technology derived... Read more
 
Copyright © 2000-2015 Globetech Media. All rights reserved.