Type
Text
Type
Dissertation
Advisor
White, Thomas W | Gergen, John | Brink, Peter | Lin, Richard | Srinivas,, Miduturu.
Date
2015-12-01
Keywords
Physiology | connexin, electrophysiology, epidermis, genetic disease, ion channel, palmoplantar keratoderma
Department
Department of Genetics.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/77633
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
Junctional-mediated intercellular communication in vertebrates is primarily achieved by clusters of connexin proteins which form gap junctions at the plasma membrane. It is believed connexins are crucial to the regulation of physiological homeostasis in various tissues such as the cochlea, and epidermis. Mutations in the GJB2 gene encoding connexin26 (Cx26) cause either deafness, or deafness associated with skin diseases. The fact that very different disorders can be caused by distinct mutations within the same gene suggests that unique channel activities are influenced by each class of mutation. We have examined the functional characteristics of two human mutations, Cx26-H73R and Cx26-S183F, causing palmoplantar keratoderma (PPK) and deafness. Both mutant proteins failed to form gap junction channels or hemichannels when expressed alone. Co-expression of the mutants with wild-type Cx43 showed a trans-dominant inhibition of Cx43 gap junction channels, without reductions in Cx43 protein synthesis. In addition, the presence of mutant Cx26 shifted Cx43 channel gating and kinetics towards a more Cx26-like behavior. Immunolocalization of Cx43 in the presence of mutant Cx26 showed a reduction of gap junction plaque formation, and resulted in a dispersal of Cx43 throughout the cell. Co-immunoprecipitation of Cx43 and mutant Cx26 showed the formation of a novel heteromeric structure that could act as a pathological unit in disrupting the stability of the epidermis. This novel formation of heteromeric Cx43 and mutant Cx26 connexons resulted in significantly increased Cx43 hemichannel activity. These findings suggest a mechanism whereby Cx26 mutations causing PPK and deafness trans-dominantly influence multiple functions of wild-type Cx43. They also implicate a role for aberrant hemichannel activity in the pathogenesis of PPK, and further highlight an emerging role for Cx43 in genetic skin diseases. While these mutants cause PPK through an interaction with Cx43, we have identified a novel Cx26 mutation, Cx26-N54H, which causes PPK through an unknown mechanism. Cx26-N54H formed functional gap junctions and hemichannels; furthermore, it did not interfere with the function of Cx43. The range of mechanisms through which Cx26 mutants cause syndromic hearing loss illustrates the functional heterogeneity of this protein. | 147 pages
Recommended Citation
Shuja, Zunaira, "Genetic alterations to Cx26 causing palmoplantar keratoderma and hearing loss modify Cx43 channel behavior" (2015). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 3428.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/3428