Structural Bases of Plexin Signal Transduction

dc.contributor.advisorChen, Zheen
dc.contributor.committeeMemberZhang, Xuewuen
dc.contributor.committeeMemberJiang, Qiu-Xingen
dc.contributor.committeeMemberChook, YuhMinen
dc.creatorPascoe, Heath Garricken
dc.date.accessioned2017-09-05T14:51:47Z
dc.date.available2017-09-05T14:51:47Z
dc.date.created2015-08
dc.date.issued2015-07-14
dc.date.submittedAugust 2015
dc.date.updated2017-09-05T14:44:39Z
dc.description.abstractPlexins are a family of transmembrane receptors for the Semaphorin family of repulsive axon guidance molecules. Plexin mediated signal transduction is critical for a variety of cellular processes including regulation of adhesion and actin organization. Aberrant plexin signaling is associated with numerous pathologies. Despite plexin's essential cellular functions, a detailed understanding of the structural basis underlying plexin singling remains elusive. Here, the structural bases for two aspects of plexin signaling are revealed. Plexins relay signals in part by accelerating the GTP hydrolysis reaction catalyzed by the small GTPase Rap. This discovery appears at odds with the known structural features of plexin GAP domains. Plexin GAPs are structurally related to RasGAPs and possess RasGAP catalytic machinery. Conversely, plexins are structurally unrelated to canonical RapGAPs and don't possess their associated catalytic machinery. Here, the structural basis underlying the non-canonical RapGAP activity of plexins is revealed. Plexins induce a unique configuration of Rap's Switch II loop to utilize a non-canonical catalytic residue. Plexins also regulate RhoA activity. The B family plexins recruit two RhoGEFs (PDZ-RhoGEF and Leukemia Associated RhoGEF) by specifically binding to the PDZ domains of these GEFs. Conversely, these PDZ domains bind promiscuously to a variety of ligands. The structural basis by which plexins specifically recognize these two PDZ domains is revealed here. B family plexins interact with the PDZ domain of PDZ-RhoGEF using a secondary interface outside the canonical PDZ binding site. This secondary interface contributes to tight binding and is important for RhoA activation following plexin activation. Secondary interfaces may be a general mechanism utilized by modular protein-protein interaction domains to achieve specificity. Structural and biochemical characterization of plexins can be difficult. Here, two methods for studying plexins are described. These methods were critical to the success of the above studies. First, a method used to generate fusion proteins in-vitro for use in crystallography is described. This method allowed for the successful crystallization of a plexin/Rap complex. Second, a biochemical assay is described for easily measuring Plexin GAP activity in-vitro. This method circumvents the difficulties of many alternative approaches to measuring GAP activity.en
dc.format.mimetypeapplication/pdfen
dc.identifier.oclc1002857192
dc.identifier.urihttps://hdl.handle.net/2152.5/4211
dc.language.isoenen
dc.subjectCell Adhesion Moleculesen
dc.subjectGuanosine Triphosphateen
dc.subjectNerve Tissue Proteinsen
dc.subjectPDZ Domainsen
dc.subjectrap GTP-Binding Proteinsen
dc.subjectRho Guanine Nucleotide Exchange Factorsen
dc.titleStructural Bases of Plexin Signal Transductionen
dc.typeThesisen
dc.type.materialtexten
thesis.degree.departmentGraduate School of Biomedical Sciencesen
thesis.degree.disciplineMolecular Biophysicsen
thesis.degree.grantorUT Southwestern Medical Centeren
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen

Files

Original bundle

Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
PASCOE-DISSERTATION-2015.pdf
Size:
78.49 MB
Format:
Adobe Portable Document Format

License bundle

Now showing 1 - 1 of 1
No Thumbnail Available
Name:
LICENSE.txt
Size:
1.84 KB
Format:
Plain Text
Description: