Rv0774c, an iron stress inducible, extracellular esterase is involved in immune-suppression associated with altered cytokine and TLR2 expression.
Tuberculosis, one of the leading cause of death from infectious diseases, is caused by Mycobacterium tuberculosis. The genome of M. tuberculosis has been sequenced and nearly 40% of the whole genome sequence was categorized as hypothetical. Rv0774c was annotated as membrane exported hypothetical protein in TB database. In silico analysis revealed that Rv0774c is a paralog of PE-PGRS multi gene family with 100 aa N-terminal domain similar to PE domain of PE-PGRS proteins. Its C-terminal domain is quite different from PGRS domain, having characteristic lipase signature GXSXG & HG and catalytic residues predicted for lipolytic activity. Therefore, DNA coding for Rv0774c (303 aa), its N-terminal (1-100 aa) and C- terminal domain (100-303 aa) were separately cloned from M. tuberculosis and were over expressed in E. coli. Rv0774c gene and its C-terminal lipolytic domain preferably hydrolyzed short chain esters. Though no enzyme activity was observed in N-terminus PE like domain, it was demonstrated to enhance the thermostability of full length Rv0774c. Tetrahydrolipstatin inhibited the enzyme activity and predicted catalytic residues (Ser-185, Asp-255 and His-281) were confirmed by site directed mutagenesis. Rv0774c was secreted out in culture media by M. tuberculosis and was up-regulated in iron limiting conditions. Treatment of THP-1 cells with rRv0774c resulted in a decline in the LPS induced production of NO and expression of iNOS. rRv0774c treated THP-1 cells also showed an enhanced expression of IL-10 and TLR2. On contrary, it suppressed the LPS induced production of IL-12, chemokines MCP-1 and IL-8. Rv0774c inhibited the LPS induced phosphorylation of p38. These observations suggested that Rv0774c could modulate the pro-inflammatory immune response to support intracellular survival of the mycobacterium.
Department of Biotechnology, Panjab University, Chandigarh 160014, India. Electronic address: surya_prbha@ymail.com.
Arbind
A
Kumar
School of Biotechnology, Banaras Hindu University, Varanasi 221005, India. Electronic address: sukhmahendrasingh@yahoo.com.
Sukh Mahendra
SM
Singh
National Centre for Human Genome Studies and Research, Panjab University, Chandigarh, India. Electronic address: ranvir1@pu.ac.in.
Ranvir
R
Singh
Department of Biotechnology, Panjab University, Chandigarh 160014, India. Electronic address: jagsekhon@pu.ac.in.
Jagdeep
J
Kaur
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002460:Cell Line; D003001:Cloning, Molecular; D016207:Cytokines / Q000037:antagonists & inhibitors*; D004252:DNA Mutational Analysis; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D004950:Esterases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D054884:Host-Pathogen Interactions; D006801:Humans; D007165:Immunosuppression Therapy; D008070:Lipopolysaccharides / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects / Q000276:immunology; D016297:Mutagenesis, Site-Directed; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000502:physiology*; D013379:Substrate Specificity; D013696:Temperature; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors*
D001426:Bacterial Proteins; D016207:Cytokines; D008070:Lipopolysaccharides; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D004950:Esterases
Esterase; Immunosuppression; M. tuberculosis; PE-PGRS multigene family; Rv0774c