Kinetics and regulation of the initial stages of cadherin-mediated adhesion

Langer, Matthew

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https://hdl.handle.net/2142/29603 Copy

Description

Title

Kinetics and regulation of the initial stages of cadherin-mediated adhesion

Author(s)

Langer, Matthew

Issue Date

2012-02-06T20:06:14Z

Director of Research (if dissertation) or Advisor (if thesis)

Leckband, Deborah E.

Committee Member(s)

• Higdon, Jonathan J.L.
• Kong, Hyun Joon
• Wang, Yingxiao

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Cadherins
• cell adhesion
• cell sorting
• N-glycosylation
• kinetics
• micropipette

Abstract

Cell adhesion plays a critical role in development, and in the maintenance of tissue integrity. Cadherins are calcium-dependent adhesion proteins which mediate cell adhesion in soft tissues. Several theories have been offered to explain the mechanism of cadherin adhesion. The first proposed mechanism put forth held that cadherins mediated binding through exchange of a tryptophan containing strand at the N-terminal domain. Another theory holds that there is an initial equilibrium which then is converted to the strand exchange form. These theories do not fully account for the range of observed experimental data, which demonstrates that there appear to be multiple binding conformations, and that lateral interactions may play a critical role in cadherin kinetics. This dissertation looks at kinetic measurements of cadherin binding which are done in the context of the cell membrane, and quantifies the affinity of the tryptophan strand exchange for three classical cadherins. Both the interactions between cadherins of the same type (homophilic), and cadherins of different types (heterophilic) are quantified. The affinity changes are then correlated with cell aggregation results, demonstrating the threshold of affinity change required to see cells segregate. Multiple cell types which express cadherin were characterized. This allowed for investigation of whether there are other factors which would be cell-line specific to alter the intrinsic affinity of the cadherin bond. To further test the ability of cadherin to mediate binding independent of other factors, the soluble portion of the protein was immobilized on the surface of a red blood cell, and the binding kinetics were observed. When cadherins are produced by the cell, carbohydrates are added to the protein backbone in a process called glycosylation. The effect that one type of glycosylation, N-glycosylation, has on cadherin kinetics was investigated. It was determined that the loss of N-glycosylation on regions of the protein not associated with the Tryptophan strand exchange can have a qualitative effect on the cadherin binding kinetics. Based upon data available in the field, this dissertation proposes a new model for cadherin binding which accounts for this finding.

Graduation Semester

2011-12

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http://hdl.handle.net/2142/29603

Copyright and License Information

Copyright 2011 Matthew Douglas Langer

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