Bacterial subversion of the host secretory pathway

An inside job: subversion of the host secretory pathway by intestinal pathogens

PURPOSE OF REVIEW

The cellular secretory pathway, composed of the endoplasmic reticulum, Golgi apparatus, and cellular vesicles, mediates the intracellular trafficking of proteins and lipids. Gastrointestinal pathogens frequently affect the functions of enterocytes, the differentiated cells involved in secretion and absorption of extracellular molecules. Microbial pathogenesis can be enhanced by altering the trafficking of key molecules such as brush border enzymes, soluble immune mediators such as cytokines and chemokines, and MHC Class I molecules, all of which rely on the secretory pathway for their appropriate cellular localization. This review focuses on our current understanding of the distinct mechanisms employed by enteric pathogens to antagonize the secretory pathway.

RECENT FINDINGS

Many pathogens encode individual or multiple proteins to antagonize the secretory pathway, including disrupting the trafficking of vesicles between the endoplasmic reticulum, Golgi, and plasma membrane. This antagonism allows for increased pathogenesis and can assist, directly or indirectly, in microbial replication. Virtually all arms of the secretory pathway are targeted by intestinal pathogens, supporting the pathogenic significance of shutting this pathway down.

SUMMARY

This review summarizes the mechanisms utilized by gut pathogens to disrupt the cellular secretory pathway and addresses potential therapeutic targets to combat these highly prevalent and burdensome microbes.

Organelle identity and the signposts for membrane traffic

Eukaryotic cells have systems of internal organelles to synthesize lipids and membrane proteins, to release secreted proteins, to take up nutrients and to degrade membrane-bound and internalized molecules. Proteins and lipids move from organelle to organelle using transport vesicles. The accuracy of this traffic depends upon organelles being correctly recognized. In general, organelles are identified by the activated GTPases and specific lipid species that they display. These short-lived determinants provide organelles with an identity that is both unique and flexible. Recent studies have helped to establish how cells maintain and restrict these determinants and explain how this system is exploited by invading pathogens.