{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/33751"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/33751","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Investigations of tetraspanin functions using large extracellular loops","abstract":"This thesis describes our characterization of a specific tetraspanin domain: the large extracellular loop (LEL). Tetraspanins are involved in cellular migration, adhesion, and metastasis, sperm-egg fusion, and viral infectivity. The large extracellular loop domain is the major extracellular domain of tetraspanins and the binding of a monoclonal antibody against the tetraspanin CD9 serves to inhibit fertilization, consistent with the CD9-null mouse model. The first area of focus in this thesis is the characterization of the murine CD9-LEL domain. We present a methodology to express and purify the mCD9-LEL to homogeneity. Biophysical characterization of the mCD9-LEL protein reveals that it is an autonomously folding, [alpha]-helical dimer. Mutagenesis over much of the mCD9-LEL protein reveals that it is composed of two subdomains: a dimerization subdomain and a variable subdomain proposed to mediate heterotypic interactions. These results suggest both a means for exploring endogenous tetraspanins functions and a mechanism by which tetraspanins may oligomerize. Surprisingly, we were not able to detect oligomerization of the intact CD9 molecule, in discordance with our biophysical data on the mCD9-LEL.","abstract_html":"This thesis describes our characterization of a specific tetraspanin domain: the large extracellular loop (LEL). Tetraspanins are involved in cellular migration, adhesion, and metastasis, sperm-egg fusion, and viral infectivity. The large extracellular loop domain is the major extracellular domain of tetraspanins and the binding of a monoclonal antibody against the tetraspanin CD9 serves to inhibit fertilization, consistent with the CD9-null mouse model. The first area of focus in this thesis is the characterization of the murine CD9-LEL domain. We present a methodology to express and purify the mCD9-LEL to homogeneity. Biophysical characterization of the mCD9-LEL protein reveals that it is an autonomously folding, [alpha]-helical dimer. Mutagenesis over much of the mCD9-LEL protein reveals that it is composed of two subdomains: a dimerization subdomain and a variable subdomain proposed to mediate heterotypic interactions. These results suggest both a means for exploring endogenous tetraspanins functions and a mechanism by which tetraspanins may oligomerize. Surprisingly, we were not able to detect oligomerization of the intact CD9 molecule, in discordance with our biophysical data on the mCD9-LEL.","abstract_has_math":false,"creators":["Liu, Christopher C"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Dept. of Biology.","school":null,"contributors":[],"advisors":["Peter S. Kim and Richard O. Hynes."],"committee_chairs":[],"committee_members":[],"year":2005,"date_issued":"2005","date_published":"2005","updated_at":"2026-07-22T22:22:31Z","subjects":["Biology."],"languages":["eng"],"rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/33751","http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://dspace.mit.edu/handle/1721.1/33751"],"render_values":[{"text":"http://dspace.mit.edu/handle/1721.1/33751","href":"http://dspace.mit.edu/handle/1721.1/33751","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/33751","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Peter S. Kim and Richard O. Hynes."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Dept. of Biology."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. 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They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/33751","http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://dspace.mit.edu/handle/1721.1/33751","http://hdl.handle.net/1721.1/33751"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2005.","Includes bibliographical references."]},{"key":"dc:description.abstract","label":"Abstract","values":["This thesis describes our characterization of a specific tetraspanin domain: the large extracellular loop (LEL). Tetraspanins are involved in cellular migration, adhesion, and metastasis, sperm-egg fusion, and viral infectivity. The large extracellular loop domain is the major extracellular domain of tetraspanins and the binding of a monoclonal antibody against the tetraspanin CD9 serves to inhibit fertilization, consistent with the CD9-null mouse model. The first area of focus in this thesis is the characterization of the murine CD9-LEL domain. We present a methodology to express and purify the mCD9-LEL to homogeneity. Biophysical characterization of the mCD9-LEL protein reveals that it is an autonomously folding, [alpha]-helical dimer. Mutagenesis over much of the mCD9-LEL protein reveals that it is composed of two subdomains: a dimerization subdomain and a variable subdomain proposed to mediate heterotypic interactions. These results suggest both a means for exploring endogenous tetraspanins functions and a mechanism by which tetraspanins may oligomerize. Surprisingly, we were not able to detect oligomerization of the intact CD9 molecule, in discordance with our biophysical data on the mCD9-LEL.","(cont.) In the latter part of this thesis, we expand our methodology to purify and characterize three different tetraspanins-LELs, the hCD9-LEL, the hCD63-LEL, and the hCD8 1-LEL. These tetraspanins-LELs all exhibit similar characteristics to the mCD9-LEL, consistent with a published crystal structure of the hCD81-LEL. Lastly, we demonstrate the ability of our tetraspanin-LEL proteins to bind integrins, to inhibit sperm-egg fusion, and to inhibit hepatitis C viral infectivity. Taken as a whole, these studies present novel, biophysically validated tetraspanins-LELs that lend insight into endogenous tetraspanins functions."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Investigations of tetraspanin functions using large extracellular loops"]}]}],"canonical_facts":{"dc:contributor.advisor":["Peter S. Kim and Richard O. Hynes."],"dc:contributor.department":["Massachusetts Institute of Technology. Dept. of Biology."],"dc:contributor.other":["Massachusetts Institute of Technology. Dept. of Biology."],"dc:creator":["Liu, Christopher C"],"dc:date.accessioned":["2008-04-24T08:53:11Z"],"dc:date.available":["2008-04-24T08:53:11Z"],"dc:date.issued":["2005"],"dc:description":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2005.","Includes bibliographical references."],"dc:description.abstract":["This thesis describes our characterization of a specific tetraspanin domain: the large extracellular loop (LEL). Tetraspanins are involved in cellular migration, adhesion, and metastasis, sperm-egg fusion, and viral infectivity. The large extracellular loop domain is the major extracellular domain of tetraspanins and the binding of a monoclonal antibody against the tetraspanin CD9 serves to inhibit fertilization, consistent with the CD9-null mouse model. The first area of focus in this thesis is the characterization of the murine CD9-LEL domain. We present a methodology to express and purify the mCD9-LEL to homogeneity. Biophysical characterization of the mCD9-LEL protein reveals that it is an autonomously folding, [alpha]-helical dimer. Mutagenesis over much of the mCD9-LEL protein reveals that it is composed of two subdomains: a dimerization subdomain and a variable subdomain proposed to mediate heterotypic interactions. These results suggest both a means for exploring endogenous tetraspanins functions and a mechanism by which tetraspanins may oligomerize. Surprisingly, we were not able to detect oligomerization of the intact CD9 molecule, in discordance with our biophysical data on the mCD9-LEL.","(cont.) In the latter part of this thesis, we expand our methodology to purify and characterize three different tetraspanins-LELs, the hCD9-LEL, the hCD63-LEL, and the hCD8 1-LEL. These tetraspanins-LELs all exhibit similar characteristics to the mCD9-LEL, consistent with a published crystal structure of the hCD81-LEL. Lastly, we demonstrate the ability of our tetraspanin-LEL proteins to bind integrins, to inhibit sperm-egg fusion, and to inhibit hepatitis C viral infectivity. Taken as a whole, these studies present novel, biophysically validated tetraspanins-LELs that lend insight into endogenous tetraspanins functions."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["http://dspace.mit.edu/handle/1721.1/33751","http://hdl.handle.net/1721.1/33751"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/33751","http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Biology."],"dc:title":["Investigations of tetraspanin functions using large extracellular loops"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:22:31Z"}