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Functional insights into the S higella type III needle tip IpaD in secretion control and cell contact
Author(s) -
Schiavolin Lionel,
Meghraoui Alaeddine,
Cherradi Youness,
Biskri Latéfa,
Botteaux Anne,
Allaoui Abdelmounaaïm
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12185
Subject(s) - secretion , effector , biology , microbiology and biotechnology , vacuole , cytosol , transport protein , cytoplasm , type vi secretion system , biochemistry , virulence , gene , enzyme
Summary Type III secretion apparatus ( T 3 SA ) are complex nanomachines that insert a translocation pore into the host cell membrane through which effector proteins are injected into the cytosol. In S higella , the pore is inserted by a needle tip complex that also controls secretion. IpaD is the key protein that rules the composition of the tip complex before and upon cell contact or C ongo red ( CR ) induction. However, how IpaD is involved in secretion control and translocon insertion remains not fully understood. Here, we report the phenotypic analysis of 20 10‐amino acids deletion variants all along the coiled‐coil and the central domains of IpaD (residues 131–332). Our results highlight three classes of T 3 S phenotype; (i) wild‐type secretion, (ii) constitutive secretion of all classes of effectors, and (iii) constitutive secretion of translocators and early effectors, but not of late effectors. Our data also suggest that the composition of the tip complex defines both the T 3 SA inducibility state and late effectors secretion. Finally, we shed light on a new aspect regarding the contact of the needle tip with cell membrane by uncoupling the Shigella abilities to escape macrophage vacuole, and to insert the translocation pore or to invade non‐phagocytic cells.