Biomolecules on cell surfaces play critical roles in diverse biological and physiological processes. However, conventional bulk scale techniques are unable to clarify the density and distribution of specific biomolecules in situ on single, living cell surfaces at the micro or nanoscale. In this work, a single cell analysis technique based on Atomic Force Microscopy (AFM) is developed to spatially identify biomolecules and characterize nanomechanical properties on single cell surfaces. The unique advantage of these AFM-based techniques lies in the ability to operate in situ (in a non-destructive fashion) and in real time, under physiological conditions or controlled micro-environments. First, AFM-based force spectroscopy was developed to study the fundamental biophysics of the heparin/thrombin interaction at the molecular level. Based on force spectroscopy, a force recognition mapping strategy was developed and optimized to spatially detect single protein targets on non-biological surfaces. This platform was then translated to the study of complex living cell surfaces. Specific carbohydrate compositions and changes in their distribution, as well as elasticity change were obtained by monitoring Bacillus cells sporulation process. The AFM-based force mapping technique was applied to different cellular systems to develop a cell surface biomolecule library. Nanoscale imaging combined with carbohydrate mapping was used to evaluate inactivation methods and growth temperatures effects on Yersinia pestis surface. A strategy to image cells in real time was coupled with hydrophobicity mapping technique to monitor the effect of antimicrobials (antimicrobial polymer and copper) on Escherichia coli and study their killing mechanisms. The single spore hydrophobicity mapping was used to localize the exosporium structure and potentially reconstruct culture media. The descriptions of cell surface DNA on single human epithelial cells potentially form a novel tool for forensic identification. Overall, these nanoscale tools to detect and assess changes in cell behavior and function over time, either as a result of natural state changes or when perturbed, will further our understanding of fundamental biological processes and lead to novel, robust methods for the analysis of individual cells. Real time analysis of cells can be used for the development of lab-on-chip type assays for drug design and testing or to test the efficacy of antimicrobials.

Candida albicans is an opportunistic fungal pathogen that may cause mucutaneous infection and/or disseminated candidasis if the host defense system is impaired (such as those in HIV patients). Cell surface of C. albicans is the frontier where initial interplay between host-pathogen takes place and therefore is of great importance in understanding the mechanism of hostpathogen interaction. MALDI-TOF-MS analysis of intact fungal cells yielded mass signatures for rapid species differentiation, strain grouping and yeast morphogenesis monitoring. Cell surface biotinylations at low temperature (4°C), enzymatic digestion of the intact fungal cell surface proteins ("whole cell shaving"), biotin-avidin affinity enrichment of biotinylated peptides, liquid chromatography mass spectrometry (LC-MS) based proteomic approach were employed for unambiguous identification of cell wall/cell wall associated proteins and the exposed peptide segments of these proteins. SILAC (Stable Isotope Labeling by Amino acids in Cell Culture) based CWP quantification analyses were performed to monitor CWP accumulation level change in response to hyphae induction. Information on surface exposed peptide segments and regulation of cell wall/surface protein during morphogenesis provided new candidates to the pool of potential peptide targets for protective vaccine development. A New type of "fluorous" (fluorinated alkane) affinity gained popularity due to its low level nonspecific protein/peptide binding. Fluorous labeling reagents that target primary amine groups in proteins/peptides were synthesized and characterized. The acid labile linker in the labeling reagents allows cleavage of the bulky fluorous tag moiety and the long oligo ethylene glycol (OEG) spacer after fluorous affinity purification. Upon collision induced decomposition, the labeled peptide ion yielded a characteristic fragment that could be retrieved from the residual portion of fluorous affinity tag, and serve as a marker to indicate that the relevant peptide had been successfully labeled. Results showed that both the protein/peptide labeling and affinity enrichment/separation process were highly efficient.

Em condições inflamatórias do sistema vascular, altas concentrações de mieloperoxidase somada à presença do ácido úrico, sugerem a formação local do oxidante hidroperóxido de urato. A ação desse peróxido já foi demonstrada sobre glutationa e peroxirredoxinas, tornando plausível a possibilidade de que outras proteínas tiólicas também pudessem ser alvo de oxidação. A proteína dissulfeto isomerase é uma ditiol-dissulfeto oxidoredutase e chaperona, localizada principalmente no retículo endoplasmático, onde participa do enovelamento de proteínas nascentes. Além disso, um pool dessas enzimas foi identificado na superfície da célula e no meio extracelular (secretada) e parece ser especialmente importante em eventos vasculares como ativação e agregação de plaquetas, trombose e remodelamento vascular. Primeiramente, foi investigado se o hidroperóxido de urato era capaz de oxidar a PDI. Pelo ensaio do DTNB foi verificado que os tióis livres da proteína eram consumidos após reação com o peróxido e, em seguida, por nLC-MS/MS os resíduos de cisteínas dos sítios catalíticos foram identificados como os principais alvos de oxidação. Embora não tenham sido verificadas outras modificações além de dissulfetos, foi observado que o tratamento com hidroperóxido promoveu agregação e inativação da proteína. Os estudos subsequentes envolveram uma linhagem de células endoteliais (HUVECs). Análises preliminares de citotoxicidade (detecção da atividade da enzima lactato desidrogenase no sobrenadante e incorporação de sondas fluorescentes ao DNA) mostraram que tratamentos com concentrações de até 400 µM de hidroperóxido de urato não são letais às células em cultura. Usando alquilantes impermeáveis à membrana celular foi mostrado que o hidroperóxido de urato oxida não só a proteína dissulfeto isomerase, mas também proteínas tiólicas totais expressas na superfície das HUVECs. Experimentos de wound healing foram feitos para avaliação da capacidade de migração das células mediante o tratamento com hidroperóxido de urato, mas nenhuma diferença foi observada. Contudo, a incubação das células com os agentes oxidantes hidroperóxido de urato e diamida, inibidores de PDI e integrina e um alquilante de tiol, resultaram, pelo menos nos trinta primeiros minutos, em menor capacidade de adesão das células à fibronectina. Além disso, as células tratadas com hidroperóxido de urato se tornaram mais sensíveis ao destacamento da placa de cultura e apresentaram alteração na morfologia. O tratamento com o peróxido também afetou a homeostase redox das HUVECs, observado pela diminuição da razão GSH/GSSG. Finalmente foram apresentadas evidênciasindiretas de que o ácido úrico é substrato da peroxidasina, uma heme peroxidase abundantemente expressa no sistema vascular. Primeiro, pelo ensaio do Amplex Red foi observado que a presença de ácido úrico na mistura reacional resultou em menor taxa de oxidação do reagente. Depois, por LC-MS/MS, também em amostra na qual o ácido úrico estava presente, foi identificado o hidroxiisourato, álcool resultante da decomposição do hidroperóxido de urato. Todo o conjunto de dados deverá contribuir para o maior entendimento da participação do hidroperóxido de urato em processos oxidativos vasculares − especialmente a oxidação de proteínas − que pode ser um dos mecanismos responsáveis pela alteração da função endotelial e da homeostase vascular. / During vascular inflammatory conditions, high amounts of myeloperoxidase added to the presence of uric acid, suggest the local formation of urate hydroperoxide. Its oxidative action has already been demonstrated on glutathione and peroxiredoxins, making plausible the possibility that other thiol proteins could also be a target for oxidation. The protein disulfide isomerase is a dithiol-disulfide oxidoreductase and chaperone, located mainly in the endoplasmic reticulum, where it is involved in the correct folding of nascent proteins. Also, a pool of these enzymes has been identified in cell surface and the extracellular (secreted) milieu and appears to be important in vascular events, such as platelet activation and aggregation, thrombosis and vascular remodeling. First, it was investigated whether urate hydroperoxide was capable of oxidizing PDI. By the DTNB assay, it was found that the free thiols of the protein were consumed after reaction with the peroxide and then, by nLC-MS / MS, the active redox cysteine residues were identified as the main oxidation targets. Although no modifications other than disulfides have been found, hydroperoxide treatment has been shown to promote protein aggregation and inactivation. Subsequent studies involved an endothelial cell line (HUVECs). Preliminary cytotoxicity analyzes (detection of lactate dehydrogenase enzyme activity in the supernatant and incorporation of fluorescent probes into DNA) have shown that treatments with concentrations up to 400 µM are not lethal to cells in culture. Then, using alkylating agents impermeable to the cell membrane, urate hydroperoxide was shown to oxidize not only PDI but also total thiol proteins expressed on HUVECs surface. Wound healing experiments were performed to evaluate cell migration after treatment with urate hydroperoxide, but no difference was observed. However, incubation of the cells with the oxidizing agents urate hydroperoxide and diamide, inhibitors of both PDI and integrin and a thiol alkylator, resulted, at least for the first thirty minutes, in reduced cell adhesion to fibronectin. In addition, cells treated with urate hydroperoxide became more sensitive to detachment from the culture dish and exhibited alterations in morphology. Treatment with the peroxide also affected the redox homeostasis of the HUVECs, observed by a decrease in the GSH / GSSG ratio. Finally, indirect evidence was presented that uric acid is a substrate of peroxidasin, a heme peroxidase abundantly expressed in the vascular system. First, with the Amplex Red assay it was observed that the presence of uric acid in the reaction mixture resulted in lower oxidation rates of the reagent. Then, by LC-MS / MS, hydroxyisourate, which is the alcohol derived from urate hydroperoxide decomposition, was also identified in samples containing uric acid. Taken together, the data presented should contribute to a better understanding of the involvement of urate hydroperoxide in vascular oxidative processes − especially protein oxidation − that may be one mechanism associated to disturbances in endothelial function and vascular homeostasis.

A total of 338 infants with suspected clinical sepsis were investigated, 115 of whom were found to be clinically infected. Twenty-one healthy term neonates were recruited as control subjects. The expression of CD64 on neutrophils in infected infants was significantly elevated at both 0 h and 24 h, compared with those of noninfected infants or controls (both p < 0.0005). The calculated optimal cutoff value for CD64 was 6136 antibody-phycoerythrin molecules bound/cell. CD64 has a very high sensitivity (96%) and NPV (97%) at 24 h. The use of CRP in combination with CD64 as predictive markers only marginally enhanced the sensitivity and NPV (97% and 98%, respectively). There was no statistical difference in the expression of monocyte HLA-DR among infected, noninfected, and control subjects. As a result, the optimal cutoff value for HLA-DR could not be determined. The technology of flow cytometry has potential applications for use in the diagnosis of neonatal sepsis because the measurement is quantitative, requiring only a minimal amount of whole blood and a short duration (within 3 h) for the provision of results. (Abstract shortened by UMI.) / Term newborns in whom infection was suspected when they were <72 h of age were recruited into the study. The expressions of CD64 on neutrophils and HLA-DR on monocytes were measured by flow cytometry at 0 h (the time of sepsis evaluation) and 24 h after the onset of presentation. A full sepsis screen, including complete blood count, serial C-reactive protein (CRP), blood culture, cerebrospinal fluid culture, and chest radiograph were performed. The demographic and clinical data were documented. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of neutrophil CD64, monocyte HLA-DR and the combination of markers for predicting neonatal sepsis were determined. / This prospective study aimed to evaluate the diagnostic utilities of two cell surface markers, neutrophil CD64 and monocyte HLA-DR, for the identification of early-onset clinical infection and pneumonia in term infants. The optimal cutoff value of each marker was defined according to the Receiver Operating Characteristic curve so that it could be used as a reference with which future studies can be compared. / Li Geng. / "May 2005." / Adviser: Pak Cheung Ng. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0174. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 129-150). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

In a HEK 293 cell line stably expressing seabream GHS-R1a (sbGHS-R1a), we found that a synthetic growth hormone secretagogue (GHS) increased [ 3H]-inositol phosphate production, clearly indicating coupling of this receptor to Gq/11-proteins. Using Western blotting, we found that GHS could also stimulate extracellular signal-regulated kinases 1 and 2 (ERK1/2), and that this response was inhibited by the MEK inhibitor U0126. For both the [3H]-inositol phosphate and ERK1/2 assays, the presence of the GHS-R antagonist D-Lys(3)-GHRP-6 significantly inhibited the GHS-stimulated activities, and in addition inhibited basal activities by 50% and 40%, respectively. These results showed that sbGHS-R1a is a constitutively active receptor and the antagonist D-Lys(3)-GHRP-6 is an inverse agonist. We also proposed that the expression of sbGHS-Rs was involved in the regulation of cell apoptosis. / Oligomerization of the human GHS-Rs (hGHS-Rs) was explored by transient transfection of the hGHS-Rs in HEK 293 cells followed by co-immunoprecipitation of differentially epitope-tagged forms of the receptors and bioluminescence resonance energy transfer 2 (BRET2) studies. (Abstract shortened by UMI.) / The concept that G protein-coupled receptors (GPCRs) exist and potentially function as dimers and/or higher oligomers has progressed from hypothesis to being widely accepted recently. Oligomerization of GPCRs has been increasingly noted in the regulation of the biological activity of the receptors. The growth hormone secretagogue receptor 1a (GHS-R1a) is a GPCR which principally regulates the pulsatile release of growth hormone from the pituitary gland. The GHS-R exists in two forms: GHS-R1a being a constitutively-active GPCR with 7 transmembrane (TM) domains, and GHS-R1b being a truncated version of type 1a but having only 5 TM domains. The endogenous agonist for GHS-R1a is ghrelin which exerts a wide range of physiological actions, but the function of GHS-R1b is still unclear. Since the tissue distribution patterns of the two isoforms of GHS-R are different, the objective of the present study is to explore the mechanisms of cell signalling of GHS-R1a and to determine the extent and importance of interactions between these two receptor isoforms. / Leung Po Ki. / "July 2005." / Adviser: Helen Wise. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3728. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 189-210). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / School code: 1307.

Yeung, Barry Ho Sing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 137-154). / Abstracts in English and Chinese. / Abstract --- p.i / 論文摘要 --- p.iv / Acknowledgements --- p.vii / Publications based on work in this thesis. --- p.ix / List of abbreviations --- p.x / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Dorsal root ganglion cells --- p.1 / Chapter 1.1.1 --- Primary sensory neurons --- p.1 / Chapter 1.1.2 --- Non-neuronal cells --- p.3 / Chapter 1.1.2.1 --- Satellite glial cells --- p.3 / Chapter 1.1.2.2 --- Schwann cells --- p.6 / Chapter 1.2 --- Peripheral sensitization --- p.8 / Chapter 1.3 --- Neuron-glia interactions --- p.9 / Chapter 1.4 --- Aim of Thesis --- p.11 / Chapter Chapter 2 --- "Materials, media, buffers and solutions" --- p.13 / Chapter 2.1 --- Materials --- p.13 / Chapter 2.2 --- "Culture media, buffer and solutions" --- p.19 / Chapter 2.2.1 --- Culture media --- p.19 / Chapter 2.2.2 --- General culture buffers and culture plate coating reagents --- p.19 / Chapter 2.3 --- Antibodies used for identifying DRG cells --- p.23 / Chapter 2.3.1 --- Primary antibodies --- p.23 / Chapter 2.3.2 --- Secondary antibodies --- p.23 / Chapter Chapter 3 --- Methods --- p.24 / Chapter 3.1 --- Preparation of DRG cell cultures --- p.24 / Chapter 3.2 --- Preparation of neuron-enriched and glial cell cultures --- p.25 / Chapter 3.3 --- Immunocytochemistry --- p.26 / Chapter 3.4 --- Immunohistochemistry --- p.27 / Chapter 3.4 --- Determination of [3H]cAMP production in DRG cells --- p.28 / Chapter 3.4.1 --- Principle of assay --- p.28 / Chapter 3.4.2 --- Loading DRG cells with [3H]adenine --- p.28 / Chapter 3.4.3 --- Column preparation --- p.28 / Chapter 3.4.4 --- Measurement of [3H]cAMP production in DRG cells --- p.29 / Chapter 3.4.5 --- Data analysis --- p.30 / Chapter Chapter 4 --- Identification of DRG cells in dissociated cultures --- p.31 / Chapter 4.1 --- Introduction --- p.31 / Chapter 4.2 --- Aim of study --- p.34 / Chapter 4.3 --- Results --- p.35 / Chapter 4.3.1 --- Identification of DRG cells in isolated cultures --- p.35 / Chapter 4.3.2 --- Activation and proliferation of glial cells in isolated cell cultures --- p.36 / Chapter 4.3.3 --- Identification of glial cells in cultures --- p.38 / Chapter 4.3.4 --- Modification of staining methods --- p.40 / Chapter 4.3.5 --- Immunohistochemistry to identify DRG cells in DRG slices --- p.42 / Chapter 4.3.6 --- Comparison of antibody staining in whole DRG and isolated DRG cells --- p.44 / Chapter 4.4 --- Discussion --- p.44 / Chapter 4.5 --- Summary --- p.53 / Chapter Chapter 5 --- Characterization of GPCRs in isolated DRG cultures --- p.69 / Chapter 5.1 --- Introduction --- p.69 / Chapter 5.1.1 --- G-protein coupled receptors --- p.69 / Chapter 5.1.2 --- Pharmacological characterization of prostanoid receptors on DRG cells --- p.73 / Chapter 5.1.3 --- Gs- and Gi/o-coupled GPCRs in DRG cells --- p.75 / Chapter 5.1.3.1 --- Gs-coupled GPCR: β-adrenoceptors --- p.76 / Chapter 5.1.3.2 --- Gs-coupled GPCR: CGRP receptors --- p.79 / Chapter 5.1.3.3 --- Gi/o-coupled GPCR: α2-adrenoceptors --- p.82 / Chapter 5.1.3.4 --- Gi/o-coupled GPCR: Cannabinoid receptors --- p.85 / Chapter 5.1.3.5 --- Gi/o-coupled GPCR: 5-HT1Areceptors --- p.88 / Chapter 5.1.3.6 --- Gi/o-coupled GPCR: opioid and opioid-receptor-like 1 receptors --- p.90 / Chapter 5.2 --- Aims of study --- p.93 / Chapter 5.3 --- Results --- p.94 / Chapter 5.3.1 --- Characterization of prostanoid receptors in isolated DRG cells --- p.94 / Chapter 5.3.2 --- Characterization of CGRP receptors in isolated DRG cells --- p.96 / Chapter 5.3.3 --- Investigation of the effect of CGRP8.37 on CGRP responses --- p.97 / Chapter 5.3.4 --- Characterization of β1-adrenoceptors in isolated DRG cells --- p.97 / Chapter 5.3.5 --- Characterization of β2-adrenoceptors in isolated DRG cells --- p.98 / Chapter 5.3.6 --- Identification of β-adrenoceptor subtype mediating isoprenaline-stimulated responses.. --- p.99 / Chapter 5.3.7 --- Characterization of α2-adrenceptors in isolated DRG cells --- p.100 / Chapter 5.3.8 --- Characterization of cannabinoid 1 receptors in isolated DRG cells ... --- p.100 / Chapter 5.3.9 --- Characterization of cannabinoid 2 receptors in isolated DRG cells --- p.101 / Chapter 5.3.10 --- Characterization of 5-HT1A receptors in isolated DRG cells --- p.101 / Chapter 5.3.11 --- Characterization of μ-opioid receptors in isolated DRG cells --- p.102 / Chapter 5.3.12 --- Characterization of opioid-receptor-like 1 receptors in isolated DRG cells --- p.102 / Chapter 5.3.13 --- Effect of nerve growth factor on DRG cells --- p.103 / Chapter 5.4 --- Discussion --- p.106 / Chapter 5.5 --- Summary --- p.114 / Chapter Chapter 6 --- Conclusion and further studies --- p.134 / References --- p.137

<p>Extracellular GRP94 can elicit both innate and adaptive immune responses by interacting with endocytic and signaling receptors on professional antigen presenting cells (pAPCs). CD91 was the first receptor proposed to facilitate GRP94-mediated immune responses. Using a GRP94 affinity matrix, a CD91 fragment was isolated from the detergent-solubilized membranes of a pAPC cell line. It was then demonstrated that CD91 ligands could inhibit GRP94-mediated peptide cross-presentation, suggesting that CD91 played a critical role in this process. While these studies implied that CD91 could function as a GRP94 endocytic receptor, later works suggested that CD91 may not recognize GRP94 at the cell surface. These opposing observations have lead to a significant controversy surrounding the identity of CD91 as an endocytic receptor for GRP94. Because the ability of CD91 to directly mediate GRP94 surface binding and uptake has not been established, the studies included in this dissertation have focused on evaluating the ability of CD91 to facilitate three processes that are necessary for GRP94-mediated peptide cross-presentation: surface binding, internalization, and processing.</p><p>These studies utilized a recombinantly-expressed N-terminal domain of GRP94 (GRP94.NTD), which was previously shown to have nearly identical biological activity to full length GRP94. The ability of CD91 to directly bind and internalize GRP94.NTD was examined using murine embryonic fibroblast (MEF) cell lines whose expression of CD91 was either reduced via siRNA, or eliminated by genetic disruption of the CD91 locus. Binding competition experiments were also conducted. Together, these studies reveal that CD91 does not directly interact with GRP94 at the cell surface. The ability of CD91 to directly facilitate GRP94 internalization was examined using various internalization and internalization competition assays. These studies demonstrated that GRP94.NTD and the CD91 ligand RAP were internalized through spatially and kinetically distinct pathways, that CD91 was not necessary for GRP94.NTD internalization, and that RAP did not inhibit GRP94 endocytosis. Together, these studies strongly suggest that CD91 does not directly facilitate GRP94 internalization. When these studies were extended to DC2.4 mouse dendritic cells, the CD91 ligand RAP reduced GRP94.NTD internalization/process by ~15%. This suggests that CD91 may indirectly facilitate GRP94 internalization in pAPC cell lines. Lastly, cross-presentation studies were utilized to examine the ability of various CD91 ligands to influence GRP94.NTD-mediated peptide cross-presentation through a post-uptake mechanism using the DC2.4/OT-1 system. Although it was discovered that DC2.4 cells can internalize and process GRP94.NTD/peptide complexes through fluid-phase endocytosis, CD91 ligands did not significantly inhibit GRP94-mediated peptide cross-presentation by DC2.4 cells. These studies demonstrate that CD91 does not play a primary role in GRP94-mediated peptide cross-presentation.</p><p>In the course of these studies, cell surface heparan sulfate proteoglycans (HSPGs) were identified as novel cell surface binding sites for GRP94.NTD on MEF cells. This conclusion was established using three distinct experimental approaches. GRP94.NTD surface binding was significantly decreased following heparin pre-treatment, following incubation with the sulfation inhibitor sodium chlorate, and following digestion with extracellular heparinase II. Conversely, these treatments did not significantly influence GRP94.NTD binding to RAW264.7 mouse macrophage-like cells. This suggested that GRP94.NTD-HSPG cell surface interactions may require the expression of a specific type of cell surface HSPG that is not expressed by RAW264.7 cells. However, additional studies strongly suggested that GRP94.NTD-HSPG cell surface interactions were mediated by the heparan sulfate-containing side chains rather than the presence of a specific cell surface HSPG core protein.</p><p>This dissertation focuses on the critical re-examination of CD91 functions in GRP94 surface binding, uptake, and cross-presentation. Together, these results clarify conflicting data on CD91 function in GRP94 surface binding and endocytosis. This dissertation also describes the identification of cell surface HSPGs as GRP94 binding sites on MEF cells. These studies extend the diversity of surface receptors that recognize of GRP94, and suggest that cell surface HSPG-dependent interactions may contribute to the biology of GRP94-elicited immune responses.</p> / Dissertation

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 114-146).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 177-181).

Regrowth in the lesioned central nervous system is impeded by inhibitory molecules including myelin-associated inhibitors (MAIs) and chondroitin sulfate proteoglycans (CSPGs). Inhibitory molecules engage neuronal cell surface receptors and activate the small GTPase RhoA in injured neurons to mediate neurite outgrowth inhibition through targeted modifications to the cytoskeleton. Inhibition of RhoA with the ribosyltransferase C3 attenuates neurite outgrowth inhibition in vitro and in vivo but the ubiquitous expression and multifunctionality of RhoA may limit the specificity of therapeutic RhoA antagonists. The hypothesis of the thesis is that molecules that functionally interact with RhoA to mediate myelin-dependent inhibition may represent more specific targets for therapeutic intervention. We have explored the contribution of two RhoA interacting proteins to the neurite outgrowth inhibitory effects of MAIs. In Chapter 2 we describe the contribution of the rho effector, Rho kinase (ROCK) to MAI responses in neurons. In Chapter 3 we identify the cytosolic phosphoprotein CRMP4b (Collapsin Response Mediator Protein 4b) as a novel RhoA binding partner that mediates neuronal responses to CNS inhibitors. By structure function analysis we have developed a molecular antagonist of CRMP4b-RhoA binding that promotes neurite outgrowth on inhibitory substrates in vitro and has the potential to be a potent and specific molecular therapeutic for spinal cord injury. In Chapter 4 we identify glycogen sythase kinase 3b (GSK3b) as an important kinase in the MAI pathway that regulates protein interactions with RhoA. This thesis provides insights into the signal transduction machinery that is engaged in response to CNS inhibitors and suggests several novel therapeutic targets to promote axon regeneration following CNS injury.