title: Expression of the ARPC4 subunit of human Arp2/3 severely affects mycobacterium tuberculosis growth and suppresses immunogenic response in murine macrophages.
abstract: BACKGROUND
  The search for molecules against Mycobacterium tuberculosis is urgent. The mechanisms facilitating the intra-macrophage survival of Mycobacterium tuberculosis are as yet not entirely understood. However, there is evidence showing the involvement of host cell cytoskeleton in every step of establishment and persistence of mycobacterial infection.
  
  
  RESULTS
  Here we show that expression of ARPC4, a subunit of the Actin related protein 2/3 (Arp2/3) protein complex, severely affects the pathogen's growth. TEM studies display shedding of the mycobacterial outer-coat. Furthermore, in infected macrophages, mycobacteria expressing ARPC4 were cleared off at a much faster rate, and were unable to mount a pro-inflammatory cytokine response. The translocation of ARPC4-expressing mycobacteria to the lysosome of the infected macrophage was also impaired. Additionally, the ARPC4 subunit was shown to interact with Rv1626, an essential secretory mycobacterial protein. Real-time PCR analysis showed that upon expression of ARPC4 in mycobacteria, Rv1626 expression is downregulated as much as six-fold. Rv1626 was found to also interact with mammalian cytoskeleton protein, Arp2/3, and enhance the rate of actin polymerization.
  
  
  CONCLUSIONS
  With crystal structures for Rv1626 and ARPC4 subunit already known, our finding lays out the effect of a novel molecule on mycobacteria, and represents a viable starting point for developing potent peptidomimetics.
authors.affiliation: Recombinant Gene Products Group, International Centre for Genetic Engineering and Biotechnology, ICGEB Campus, Aruna Asaf Ali Marg, New Delhi, India.
authors.forename: Anamika
authors.initials: A
authors.lastname: Ghosh
authors.forename: Sultan
authors.initials: S
authors.lastname: Tousif
authors.forename: Debapriya
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: Sachin K
authors.initials: SK
authors.lastname: Samuchiwal
authors.forename: Kuhulika
authors.initials: K
authors.lastname: Bhalla
authors.forename: Megha
authors.initials: M
authors.lastname: Tharad
authors.forename: Sushil
authors.initials: S
authors.lastname: Kumar
authors.forename: Prem
authors.initials: P
authors.lastname: Prakash
authors.forename: Purnima
authors.initials: P
authors.lastname: Kumar
authors.forename: Gobardhan
authors.initials: G
authors.lastname: Das
authors.forename: Anand
authors.initials: A
authors.lastname: Ranganathan
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000737:chemistry*; D000199:Actins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival; D046508:Culture Techniques; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D007108:Immune Tolerance; D008264:Macrophages / Q000166:cytology / Q000276:immunology*; D008297:Male; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics*
chemical_list: C581326:ARPC4 protein, human; D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D001426:Bacterial Proteins; D021122:Protein Subunits
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