Show simple item record

dc.contributor.advisorNeal Silverman, Ph.D.
dc.contributor.authorAggarwal, Kamna
dc.date2022-08-11T08:08:42.000
dc.date.accessioned2022-08-23T16:05:00Z
dc.date.available2022-08-23T16:05:00Z
dc.date.issued2010-03-29
dc.date.submitted2010-06-01
dc.identifier.doi10.13028/69q1-d386
dc.identifier.urihttp://hdl.handle.net/20.500.14038/31794
dc.description.abstractInnate immunity is the first line of defense against invading pathogens. It functions to eliminate pathogens and also to control infections. The innate immune response is also important for the development of pathogen-specific adaptive immune responses. As a result, the study of innate immune signaling pathways is crucial for understanding the interactions between host and pathogen. Unlike mammals, insects lack a classical adaptive immune response and rely mostly on innate immune responses. Innate immune mechanisms have been widely studied in the fruit fly, Drosophila melanogaster. The genetic and molecular tools available in the Drosophila system make it an excellent model system for studying immunity. Furthermore, the innate immune signaling pathways used by Drosophila show strong homology to those of vertebrates making them ideal for studying these pathways. Drosophila immunity relies on cellular and humoral innate immune responses to fight pathogens. The hallmark of the Drosophilahumoral immune response is the rapid induction of antimicrobial peptide genes in the fat body. The production of these antimicrobial peptides is regulated by two immune signaling pathways-Toll and Immune Deficency (IMD) pathways. The Toll pathway responds to many Gram-positive bacterial and fungal infections , while the IMD pathway is potently activated by DAP-type peptidoglycan (PGN) from Gram-negative bacteria and certain Gram-positive bacteria. Two receptors, PGRP-LC and PGRP-LE, are able to recognize DAP-type PGN at the cell surface or in the cytosol, respectively, and trigger the IMD pathway. Upon binding DAP-type PGN, both PGRP-LC and PGRP-LE dimerize/ multimerize and signal to the downstream components of IMD pathway. It is unclear how the receptor activates its downstream components. My work has focused on understanding the molecular events that take place at the receptors following there activation. In these studies I have identified a common motif in the N-terminal domains of both the receptors, known as the RHIM-like domain. The RHIM-like domain is critical for signaling by either receptor, but the mechanism(s) involved remain unclear. IMD, a downstream component of the pathway, associates with both PGRP-LC and -LE but the interaction of PGRP-LC with IMD is not mediated through its RHIM-like domain. Also, mutations affecting the PGRP-LC RHIM-like motif are defective in all known downstream signaling events. However, the RHIM-like mutant receptors are capable of serving as a platform for the assembly of all known components of a receptor proximal signaling complex. These results suggest that another, unidentified component of the IMD signaling pathway may function to mediate interaction with the RHIM-like motif. I performed a yeast two-hybrid screen to identify proteins that might interact with the receptor PGRP-LC through its RHIM- like domain. With this approach, two new components of the IMD pathway were identified. The first component I characterized is called Rudra and it is a critical feedback inhibitor of peptidoglycan receptor signaling. The other factor is known as RYBP, it includes a highly conserved ubiquitin binding motif (NZF), and RNAi studies suggest it is a critical component of the IMD pathway. The identification and characterization of these two new components of the IMD pathway has provided a new insight into the molecular events that take place proximal to the receptor.
dc.language.isoen_US
dc.rightsCopyright is held by the author, with all rights reserved.
dc.subjectImmunity
dc.subjectInnate
dc.subjectDrosophila melanogaster
dc.subjectDrosophila Proteins
dc.subjectIntracellular Signaling Peptides and Proteins
dc.subjectSignal Transduction
dc.subjectAdaptor Proteins
dc.subjectSignal Transducing
dc.subjectReceptors
dc.subjectCell Surface
dc.subjectAmino Acids, Peptides, and Proteins
dc.subjectCells
dc.subjectGenetic Phenomena
dc.subjectHemic and Immune Systems
dc.subjectImmunity
dc.titleA View of the IMD Pathway from the RHIM
dc.typeDoctoral Dissertation
dc.identifier.legacyfulltexthttps://escholarship.umassmed.edu/cgi/viewcontent.cgi?article=1464&context=gsbs_diss&unstamped=1
dc.identifier.legacycoverpagehttps://escholarship.umassmed.edu/gsbs_diss/463
dc.legacy.embargo2011-05-26T00:00:00-07:00
dc.identifier.contextkey1338108
refterms.dateFOA2022-08-24T04:24:53Z
html.description.abstract<p>Innate immunity is the first line of defense against invading pathogens. It functions to eliminate pathogens and also to control infections. The innate immune response is also important for the development of pathogen-specific adaptive immune responses. As a result, the study of innate immune signaling pathways is crucial for understanding the interactions between host and pathogen. Unlike mammals, insects lack a classical adaptive immune response and rely mostly on innate immune responses.</p> <p>Innate immune mechanisms have been widely studied in the fruit fly, <em>Drosophila melanogaster</em>. The genetic and molecular tools available in the <em>Drosophila</em> system make it an excellent model system for studying immunity. Furthermore, the innate immune signaling pathways used by <em>Drosophila</em> show strong homology to those of vertebrates making them ideal for studying these pathways. <em>Drosophila</em> immunity relies on cellular and humoral innate immune responses to fight pathogens. The hallmark of the <em>Drosophila</em>humoral immune response is the rapid induction of antimicrobial peptide genes in the fat body. The production of these antimicrobial peptides is regulated by two immune signaling pathways-Toll and Immune Deficency (IMD) pathways.</p> <p>The Toll pathway responds to many Gram-positive bacterial and fungal infections , while the IMD pathway is potently activated by DAP-type peptidoglycan (PGN) from Gram-negative bacteria and certain Gram-positive bacteria. Two receptors, PGRP-LC and PGRP-LE, are able to recognize DAP-type PGN at the cell surface or in the cytosol, respectively, and trigger the IMD pathway. Upon binding DAP-type PGN, both PGRP-LC and PGRP-LE dimerize/ multimerize and signal to the downstream components of IMD pathway. It is unclear how the receptor activates its downstream components.</p> <p>My work has focused on understanding the molecular events that take place at the receptors following there activation. In these studies I have identified a common motif in the N-terminal domains of both the receptors, known as the RHIM-like domain. The RHIM-like domain is critical for signaling by either receptor, but the mechanism(s) involved remain unclear. IMD, a downstream component of the pathway, associates with both PGRP-LC and -LE but the interaction of PGRP-LC with IMD is not mediated through its RHIM-like domain. Also, mutations affecting the PGRP-LC RHIM-like motif are defective in all known downstream signaling events. However, the RHIM-like mutant receptors are capable of serving as a platform for the assembly of all known components of a receptor proximal signaling complex. These results suggest that another, unidentified component of the IMD signaling pathway may function to mediate interaction with the RHIM-like motif.</p> <p>I performed a yeast two-hybrid screen to identify proteins that might interact with the receptor PGRP-LC through its RHIM- like domain. With this approach, two new components of the IMD pathway were identified. The first component I characterized is called Rudra and it is a critical feedback inhibitor of peptidoglycan receptor signaling. The other factor is known as RYBP, it includes a highly conserved ubiquitin binding motif (NZF), and RNAi studies suggest it is a critical component of the IMD pathway. The identification and characterization of these two new components of the IMD pathway has provided a new insight into the molecular events that take place proximal to the receptor.</p>
dc.identifier.submissionpathgsbs_diss/463
dc.contributor.departmentMedicine
dc.description.thesisprogramInterdisciplinary Graduate Program


Files in this item

Thumbnail
Name:
Aggarwal_Kamna_reduced.pdf
Size:
3.499Mb
Format:
PDF

This item appears in the following Collection(s)

Show simple item record