Biology:Guard theory

From HandWiki

Guard theory is a branch of immunology which concerns the innate sensing of stereotypical consequences of a virulence factor or pathogen.[1] This is in contrast to the classical understanding of recognition by the innate immune system, which involves recognition of distinct microbial structures- pathogen-associated molecular patterns (PAMPs)- with pattern recognition receptors (PRRs). Some of these stereotypical consequences of virulence factors and pathogens may include altered endosomal trafficking and changes in the cytoskeleton.[2] These recognition mechanisms would work to complement classical pattern recognition mechanisms.[3][4]

Mechanism

In plants

In plants, guard theory is also known as indirect recognition.[5] This is because rather than direct recognition of a virulence factor or pathogen, there is instead recognition of the end result of a process mediated by a virulence factor or pathogen.[6] In these cases, the virulence factor appears to target an accessory protein that is either a target or a structural mimic of the target of that virulence factor,[7] allowing for plant defences to respond to a specific strategy of pathogenesis rather structures that may evolve and change over time at a faster rate than the plant can adapt to.[8] The interaction between pathogen and accessory protein results in some modification of the accessory protein, which allows for recognition by plant NBS-LRR proteins, which monitor for infection.[9] This model is best illustrated by RIN4 protein in A. thaliana.[10] RIN4 forms a complex with the NB-LRR proteins RPM1 and RPS2.[11][12] Protease effector AvrRpt2 is able to degrade RIN4, causing de-repression of RPS2.[13] On the other hand, AvrB or AvrRPM1-mediated phosphorylation of RIN4 results in activation of RPM1.[14] In short, this example elucidates how one NBS-LRR protein is able to recognize the effects of more than one virulence factor or effector.[15]

Guard defences in humans and relationship with allergies

Little is known concerning guard receptors in humans. One example currently under speculation involves recognition of cysteine proteases secreted by helminths during infection.[16] It has been speculated that some allergies develop as a result of structural similarities between the allergen and high-activity cysteine proteases secreted by helminths during their infectious cycle.[17] One proposed mechanism by which this may take place is that proteases secreted by the helminths cleave proteins which act as detectors, and these detectors in turn activate sensors to alert the immune system.[18]

References

  1. ↑ Medzhitov, R. (2011). "Innovating immunology: an interview with Ruslan Medzhitov". Disease Models & Mechanisms 4 (4): 430–432. doi:10.1242/dmm.008151. PMID 21708899. 
  2. ↑ Medzhitov, R. (2011). "Innovating immunology: an interview with Ruslan Medzhitov". Disease Models & Mechanisms 4 (4): 430–432. doi:10.1242/dmm.008151. PMID 21708899. 
  3. ↑ Innovating (2011). "an interview with Ruslan Medzhitov". Disease Models & Mechanisms 4 (4): 430–432. doi:10.1242/dmm.008151. PMID 21708899. 
  4. ↑ Kagan, Jonathan C. (October 2014). "Common mechanisms activate plant guard receptors and TLR4". Trends in Immunology 35 (10): 454–456. doi:10.1016/j.it.2014.08.009. PMID 25224694. 
  5. ↑ Dodds, Peter N.; Rathjen, John P. (2010). "Plant immunity: towards an integrated view of plant-pathogen interactions". Nature Reviews Genetics 11 (8): 539–48. doi:10.1038/nrg2812. PMID 20585331. 
  6. ↑ Dodds, Peter N.; Rathjen, John P. (2010). "Plant immunity: towards an integrated view of plant-pathogen interactions". Nature Reviews Genetics 11 (8): 539–48. doi:10.1038/nrg2812. PMID 20585331. 
  7. ↑ van der Hoorn, R. A.; Kamoun, S. (2008). "From guard to decoy: a new model for perception of plant pathogen effectors". Plant Cell 20 (8): 2009–2017. doi:10.1105/tpc.108.060194. PMID 18723576. 
  8. ↑ Dodds, Peter N.; Rathjen, John P. (2010). "Plant immunity: towards an integrated view of plant-pathogen interactions". Nature Reviews Genetics 11 (8): 539–48. doi:10.1038/nrg2812. PMID 20585331. 
  9. ↑ Zhou T, Wang Y, Chen JQ, Araki H, Jing Z, Jiang K, Shen J, Tian D: Genome-wide identification of NBS genes in japonica rice reveals significant expansion of divergent non-TIR NBS-LRR genes. Mol Genet Genomics 2004, 271:402-415.
  10. ↑ Dodds, Peter N.; Rathjen, John P. (2010). "Plant immunity: towards an integrated view of plant-pathogen interactions". Nature Reviews Genetics 11 (8): 539–48. doi:10.1038/nrg2812. PMID 20585331. 
  11. ↑ Mackey, D.; Holt, B. F.; Wiig, A.; Dangl, J. L. (2002). "RIN4 interacts with Pseudomonas syringae type 111 effector molecules and is required for RPM1-mediated resistance in Arabidopsis". Cell 108 (6): 743–754. doi:10.1016/s0092-8674(02)00661-x. PMID 11955429. 
  12. ↑ Mackey, D.; Belkhadir, Y.; Alonso, J. M.; Ecker, J. R.; Dangl, J. L. (2003). "Arabidopsis RIN4 is a target of the type 111 virulence effector AvrRpt2 and modulates RPS2-mediated resistance". Cell 112 (3): 379–389. doi:10.1016/s0092-8674(03)00040-0. PMID 12581527. 
  13. ↑ Mackey, D.; Holt, B. F.; Wiig, A.; Dangl, J. L. (2002). "RIN4 interacts with Pseudomonas syringae type 111 effector molecules and is required for RPM1-mediated resistance in Arabidopsis". Cell 108 (6): 743–754. doi:10.1016/s0092-8674(02)00661-x. PMID 11955429. 
  14. ↑ Mackey, D.; Belkhadir, Y.; Alonso, J. M.; Ecker, J. R.; Dangl, J. (2003). "Arabidopsis RIN4 is a target of the type 111 virulence effector AvrRpt2 and modulates RPS2-mediated resistance". Cell 112 (3): 379–389. doi:10.1016/s0092-8674(03)00040-0. PMID 12581527. 
  15. ↑ Dodds, Peter N.; Rathjen, John P. (2010). "Plant immunity: towards an integrated view of plant-pathogen interactions". Nature Reviews Genetics 11 (8): 539–48. doi:10.1038/nrg2812. PMID 20585331. 
  16. ↑ Capron, M; Trottein, F (2006). "Parasites and Allergy". Chem Immunol Allergy 90: 45–64. doi:10.1159/000088880. PMID 16210902. 
  17. ↑ Medzhitov, R. (2011). "Innovating immunology: an interview with Ruslan Medzhitov". Disease Models & Mechanisms 4 (4): 430–432. doi:10.1242/dmm.008151. PMID 21708899. 
  18. ↑ Medzhitov, R. (2011). "Innovating immunology: an interview with Ruslan Medzhitov". Disease Models & Mechanisms 4 (4): 430–432. doi:10.1242/dmm.008151. PMID 21708899. 



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