Pathogenesis by mycobacteria requires the exploitation of host-cell signalling pathways to enhance the intracellular survival and persistence of the pathogen. The disruption of these pathways by mycobacteria causes impaired maturation of phagosomes into phagolysosomes, modulates host-cell apoptotic pathways and suppresses the host immune response

1. Adaptations of mycobacteria for
survival in macrophages
Sameer Tiwari

4. Interaction of macrophage with mycobacteria
Peters J., Cell Host & Microbe, 2008

5. Cells involved in Phagocytosis
Monocyte
Kuby., Immunology, 4th Edi
Macrophage
Dendritic cell

6. Phagocytosis of a bacterium
Kuby, Immunology, Edi 4th

7. M. tuberculosis recognition by membrane-bound receptors
O. Neyrolles, C. Guilhot ,Tuberculosis 91 (2011) 187-195

8. Entry of M. tuberculosis in macrophage
Phagocytosis of M.tb involves different receptors on the phagocytic cell
which either bind to nonopsonized M.tb or recognize opsonins on the
surface of M.tb.
Complement receptors (CRl, CR2, CR3 and CR4), mannose receptors
(MR), CD14 receptor, collectins, scavenger receptors play important roles
in binding of the organisms to the phagocytes (Schlesinger et
al., 1996, Hoheisel et al., 1995, Gaynor et al., 1995).
Mycobacteria can invade host macrophages after opsonization with
complement factor C3, which is followed by binding and uptake through
CR1, CR3, and CR4 (Aderem et al., 1999, Hirsch et al., 1994, Schlesinger
et al., 1993). In the absence of CR3, phagocytosis of M.tb by human
macrophages and monocytes is reduced by approximately 70 to 80% in
vitro (Schlesinger et al., 1993, Schlesinger et al., 1990).

9. Inhibition of phagosomal maturation
01
Phagosome-lysosome fusion block
02
Incomplete Luminal acidification
03
Absence of proton -ATPase
04
Absence of mature lysosomal hydrolase

10. Rab effectors & mycobacterial phagolysosomes
Rab5 & 7
EEA1
LAMP1
Cathepsin D
TACO

11. Role of Ca2+ in phagosomal maturation
Ca2+- binding protein calmodulin
recruitment of the PI3K hVPS34
interference with Ca2+ fluxes by LAM

13. PI3P and phagosomal maturation
Vergne I,et al,Traffic 2003;4:600–606

14. Other host mechanisms altered by mycobacteria
Antigen processing and presentation

15. Generation of ROI & RNI
MacMicking Nature Medicine 14, 809 - 810 (2008)

16. Vandal OH et al,JOURNAL OF BACTERIOLOGY, Aug. 2009, p. 4714–4721

17. Modulation of macrophage signaling by mycobacteria
Modulation of MAPK Signalling
& JAK/STAT signalling

18. Mycobacteria alter
host apoptotic
pathways

19. Manipulation of host cell actin dynamics
Actin forms part of the eukaryotic cytoskeletal network
Migration
Memabrane ruffling
Cellular adherence

20. Activity of Coronin 1 in Macrophages

21. Protein Kinases
500 kinases
2% of all
proteins
Human geome conatins
30% of all proteins
modified by kinase activity
Phosphorylation occurs on
serine, threonine &
tyrosine residues
Variety of
cellular
processes
Including
protein
trafficking

22. Protein Kinase C

23. Role of PKC in macrophage functions
Production of
cytokines, chemokine
s and immune effector
molecule

24. Role of PKC in mycobacterial infection
Reduced activation of MAP Kinases
Decreased production of NOS2 and TNF-α

25. Serine/Threonine Protein Kinases of Mtb

26. Model for Mtb receptor STPK regulation
Alber T, Current Opinion in Structural Biology 2009,19:650–65

27. Structural analysis of M.tb STPKs

29. PknA
phosphorylate FtsZ
Impairment in GTPase activity of FtsZ

30. PknB
Functional STPK
expressed in active TB
infection
Slow growth & cell
morphology (cell shape)

31. PknD
Anchoring sensor domain
phosphorylate
MmpL7
Virulence
MmpL7 is essential for virulence, it transports polyketide virulence
factors such as phthiocerol dimycocerosate (PDIM) to the cell wall

32. PknE
Transduction
of external
signals

33. PknF
Regulation
in Glucose
transport
Slow cell
growth
Septum
formation

34. PknH
Phosphorylation of EmbR (phosphoprotein recognition domain)
DNA binding activity towards promoter regions of embCAB genes
Differential expression of a mycobacterial kinase in response to stress
conditions which can indicate its ability to regulate cellular events promoting
bacterial adaptation to environmental change i.e. low pH & heat shock

35. PknK
Regulate the expression of the mycobacterial monooxygenase (mymA) operon
Expression of mymA operon genes is regulated through PknK-mediated
phosphorylation of VirS
Phosphorylates FabD

36. PknG
Interfere with host signal transduction processes
Cellular glutamate and glutamine levels
Phosphorylate protein(s) possibly involved in host trafficking pathways
Blocking the maturation of mycobacterial phagosome into lysosomes
Establishment of an intracellular infection by blocking phagosomelysosomal fusion within macrophages
Phosphorylated GarA (glutamate metabolism)

37. PknG in mycobacterial trafficking in macrophages

38. Conclusion
Knowledge of the mycobacterial tactics for survival inside macrophages
might help not only to control tuberculosis and other mycobacterial
diseases but also to uncover novel aspects of host cell biology
Mycobacterial gene products that disrupt host defences during infection
represent potential drug targets.
Further studies, with the help of new techniques in genomics and
proteomics, will elucidate the precise mechanisms by which pathogenic
mycobacteria are able to downregulate host-signalling pathways involving
TLRs, MAPKs and JAK/STATs.
Mycobacterial Kinases could be potential targets for the development of
new TB drugs

39. THANKS