Molecular Approaches to Identifying Type 3 Secreted Effectors: a Shigella Case Study
Analise Z. Reeves, Sonia C. Costa and Cammie F. Lesser
from: Shigella: Molecular and Cellular Biology (Edited by: William D. Picking and Wendy L. Picking). Caister Academic Press, U.K. (2016) Pages: 259-276.
Type 3 secretion systems are specialized machines common to plant and animal bacterial pathogens as well as insect endosymbionts that act to deliver tens of proteins directly from bacteria into eukaryotic cells. While protein components of these complex machines are highly conserved, each bacterium delivers its own unique repertoire of proteins, commonly referred to as effectors, into host cells. The function of effectors can be difficult to identify experimentally, as they often act in a functionally redundant manner to mediate specific steps in pathogenesis such that loss of expression of an individual protein does not result in a detectable phenotype. In addition, despite the growing availability of annotated bacterial genome sequences, effectors are challenging to identify via bioinformatic approaches as they have poorly defined secretion sequences and commonly do not share homology with other proteins. Extensive efforts over the past 30-40 years have been extended towards identifying these secreted virulence proteins, and discerning how they act to usurp host cell processes to promote bacterial survival and spread. Here, we provide a historical review of the means by which the currently known ~30 Shigella effectors were discovered to illustrate the variety of experimental approaches including genetic, biochemical, functional and bioinformatic based assays that have been used to identify these important virulence factors read more ...