title: Mycobacterium tuberculosis cyclophilin A uses novel signal sequence for secretion and mimics eukaryotic cyclophilins for interaction with host protein repertoire.
abstract: Cyclophilins are prolyl isomerases with multitude of functions in different cellular processes and pathological conditions. Cyclophilin A (PpiA) of Mycobacterium tuberculosis is secreted during infection in intraphagosomal niche. However, our understanding about the evolutionary origin, secretory mechanism or the interactome of M. tuberculosis PpiA is limited. This study demonstrates through phylogenetic and structural analyses that PpiA has more proximity to human cyclophilins than the prokaryotic counterparts. We report a unique N-terminal sequence (MADCDSVTNSP) present in pathogenic mycobacterial PpiA and absent in non-pathogenic strains. This sequence stretch was shown to be essential for PpiA secretion. The overexpression of full-length PpiA from M. tuberculosis in non-pathogenic Mycobacterium smegmatis resulted in PpiA secretion while truncation of the N-terminal stretch obstructed the secretion. In addition, presence of an ESX pathway substrate motif in M. tuberculosis PpiA suggested possible involvement of Type VII secretion system. Site-directed mutagenesis of key residues in this motif in full-length PpiA also hindered the secretion in M. smegmatis. Bacterial two-hybrid screens with human lung cDNA library as target were utilized to identify interaction partners of PpiA from host repertoire, and a number of substrates with functional representation in iron storage, signal transduction and immune responses were detected. The extensive host interactome coupled with the sequence and structural similarity to human cyclophilins is strongly suggestive of PpiA being deployed by M. tuberculosis as an effector mimic against the host cyclophilins.
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India ; Department of Microbiology, University of Delhi, Delhi, India.
authors: Asani
authors: A
authors: Bhaduri
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Richa
authors: R
authors: Misra
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Abhijit
authors: A
authors: Maji
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Preetida J
authors: PJ
authors: Bhetaria
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Sonakshi
authors: S
authors: Mishra
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Gunjan
authors: G
authors: Arora
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Lalit Kumar
authors: LK
authors: Singh
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Neha
authors: N
authors: Dhasmana
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Neha
authors: N
authors: Dubey
authors: Department of Microbiology, University of Delhi, Delhi, India.
authors: Jugsharan Singh
authors: JS
authors: Virdi
authors: CSIR-Institute of Genomics and Integrative Biology, Delhi, India.
authors: Yogendra
authors: Y
authors: Singh
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D021984:Cyclophilin A / Q000235:genetics* / Q000378:metabolism*; D021983:Cyclophilins / Q000378:metabolism*; D054884:Host-Pathogen Interactions / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000472:pathogenicity*; D021382:Protein Sorting Signals / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D021382:Protein Sorting Signals; D021984:Cyclophilin A; D021983:Cyclophilins