Adhesion, Invasion, and Agglutination Mediated by Two Trimeric Autotransporters in the Human Uropathogen Proteus mirabilis

Abstract

Fimbriae of the human uropathogen Proteus mirabilis are the only characterized surface proteins that contribute to its virulence by mediating adhesion and invasion of the uroepithelia. PMI2122 (AipA) and PMI2575 (TaaP) are annotated in the genome of strain HI4320 as trimeric autotransporters with "adhesinlike" and "agglutinating adhesin-like" properties, respectively. The C-terminal 62 amino acids (aa) in AipA and 76 aa in TaaP are homologous to the translocator domains of YadA from Yersinia enterocolitica and Hia from Haemophilus influenzae. Comparative protein modeling using the Hia three-dimensional structure as a template predicted that each of these domains would contain four antiparallel beta sheets and that they formed homotrimers. Recombinant AipA and TaaP were seen as ϳ28 kDa and ϳ78 kDa, respectively, in Escherichia coli, and each also formed high-molecular-weight homotrimers, thus supporting this model. E. coli synthesizing AipA or TaaP bound to extracellular matrix proteins with a 10-to 60-fold-higher level of affinity than the control strain. Inactivation of aipA in P. mirabilis strains significantly (P < 0.01) reduced the mutants' ability to adhere to or invade HEK293 cell monolayers, and the functions were restored upon complementation. A 51-aa-long invasin region in the AipA passenger domain was required for this function. E. coli expressing TaaP mediated autoagglutination, and a taaP mutant of P. mirabilis showed significantly (P < 0.05) more reduced aggregation than HI4320. Gly-247 in AipA and Gly-708 in TaaP were indispensable for trimerization and activity. AipA and TaaP individually offered advantages to P. mirabilis in a murine model. This is the first report characterizing trimeric autotransporters in P. mirabilis as afimbrial surface adhesins and autoagglutinins.

A Naturally Occurring Single-Residue Mutation in the Translocator Domain of Neisseria meningitidis NhhA Affects Trimerization, Surface Localization, and Adhesive Capabilities

“…The trimeric autotransporter adhesin (TAA) family contains a continually increasing number of adhesins of Gram-negative bacteria (5,12), such as Yersinia enterocolitica YadA (23); Moraxella catarrhalis UspA1 and UspA2 (4); H. influenzae Hia, Hsf, and HadA (6,27,29); N. meningitidis NadA (2); Bartonella henselae BadA (22); and Proteus mirabilis AipA and TaaP (1). TAAs have a head-stalk-anchor architecture (14) and are characterized by the ability to form highly stable trimers on the bacterial surface (6).…”

Self-Transmissibility of the Integrative and Conjugative Element ICEPm1between Clinical Isolates Requires a Functional Integrase, Relaxase, and Type IV Secretion System

“…Genes for a putative tyrosine-like recombinase, a putative helicase that could act as a relaxase, and a putative T4SS were all identified in this element by in silico analysis (13). Known cargo genes that are interspersed between the core modules of ICEPm1 encode a yersiniabactin-related iron acquisition system and an adhesin/protease that both contribute to virulence in the mouse model of ascending urinary tract infection (1,19,31). ICEPm1 was present in all P. mirabilis urinary isolates yet was heterogeneously distributed in commensal P. mirabilis strains that colonize other body sites (13).…”

Transcriptome of Proteus mirabilis in the Murine Urinary Tract: Virulence and Nitrogen Assimilation Gene Expression

“…Two of these, MR/P (8) and PMF (49,86), have been shown to play a role in virulence during experimental UTI and have been the focus of vaccine efforts (39,66). Other known virulence factors for this organism include flagella (3,51), toxins (HpmAB) (77,80), proteases (Zap [83] and Lon [13]), autotransporters (Pta [2] and AipA and TaaP [1]), iron (27,42) and zinc (59) uptake, and capsule (16). Signaturetagged mutagenesis studies have also highlighted the importance of central metabolism in the disease process (12,26).…”