| dc.identifier.uri | http://hdl.handle.net/11401/77629 | |
| dc.description.sponsorship | This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. | en_US |
| dc.format | Monograph | |
| dc.format.medium | Electronic Resource | en_US |
| dc.language.iso | en_US | |
| dc.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dc.type | Dissertation | |
| dcterms.abstract | Connexin (Cx) proteins form intercellular gap junction channels to facilitate the exchange of ions and second messengers between adjacent cells. Mutations in connexins cause several human diseases by interrupting cell-to-cell communication and coupling. Connexins also form functional hemichannels in nonjunctional membranes that have an unclear role in normal physiology but have altered activity in pathological states. Mutations in <italic>GJB2</italic>, the gene encoding connexin26 (Cx26), are linked to sensorineural hearing loss as well as syndromic deafness associated with skin disorders. In contrast to Cx26 mutations causing nonsyndromic deafness, those that also cause skin disease are exclusively gain-of-function single amino acid changes with autosomal dominant inheritance patterns. At least 10 missense mutations clustered toward the N-terminus and first extracellular loop of Cx26 have been linked to keratitis-ichthyosis-deafness (KID) syndrome, which can consist of life threatening skin phenotypes. Functional changes related to hemichannel open probability and/or permeability have been shown for all but one of the tested KID-causing Cx26 mutations by both electrophysiology and dye transfer assays, and in varied expression systems. We, and others, hypothesize that hemichannel overactivity, resulting from mutations that precipitate failures in Cx26 channel regulation, undermines coordinated keratinocyte proliferation and differentiation in the epidermis. <italic>In vitro</italic> expression of mutant hemichannels causes cellular dysfunction and accelerated death, both in <italic>Xenopus laevis</italic> oocytes and mammalian cell culture, possibly because constitutively active or leaky hemichannels deplete the cells of important metabolites, such as ATP and cAMP. Additionally, imbalances in intracellular-extracellular ionic gradients may disrupt paracrine signaling pathways or cause injurious osmotic pressures. Pharmacological tools to modulate Cx26 channels are needed to assess the consequences of excessive hemichannel openings on cell viability and tissue integrity. We used two different electrophysiological assays for quantitative evaluation of prospective small molecule inhibitors of mutant Cx26 hemichannels present in KID syndrome, with an extracellular divalent cation, zinc (Zn<super>++</super>), as a positive control for comparison. Mefloquine, and related quinine-family small molecule analogs, emerged as viable candidates, capable of attenuating aberrant Cx26 hemichannel currents at low micromolar doses. Our data revealed differential drug affinities for mutant channels containing distinct biochemical modifications and underscored the need for screening against specific forms present in human disease. In this body of work, we have identified potent Cx26 hemichannel inhibitors with adequate specificity and selectivity properties to appraise the pathogenic culpability of dysregulated hemichannels in KID syndrome. Minimally, our findings support the use of these agents to further structure-function analyses aimed at elucidating the molecular bases of errors in gating and permeation that accompany mutations. Furthermore, we show that select inhibitors are particularly well positioned for testing in an inducible transgenic mouse model of the lethal form of the disease, and may demonstrate therapeutic utility in KID syndrome and other connexin-associated gain-of-function disorders. | |
| dcterms.available | 2017-09-20T16:53:05Z | |
| dcterms.contributor | White, Thomas W | en_US |
| dcterms.contributor | Thomsen, Gerald | en_US |
| dcterms.contributor | Lin, Richard | en_US |
| dcterms.contributor | Brink, Peter | en_US |
| dcterms.contributor | Srinivas, Miduturu. | en_US |
| dcterms.creator | Levit, Noah Alexander | |
| dcterms.dateAccepted | 2017-09-20T16:53:05Z | |
| dcterms.dateSubmitted | 2017-09-20T16:53:05Z | |
| dcterms.description | Department of Genetics. | en_US |
| dcterms.extent | 115 pg. | en_US |
| dcterms.format | Application/PDF | en_US |
| dcterms.format | Monograph | |
| dcterms.identifier | http://hdl.handle.net/11401/77629 | |
| dcterms.issued | 2014-12-01 | |
| dcterms.language | en_US | |
| dcterms.provenance | Made available in DSpace on 2017-09-20T16:53:05Z (GMT). No. of bitstreams: 1
Levit_grad.sunysb_0771E_11758.pdf: 30261981 bytes, checksum: 6b2649c69c8f60e6893e608d460b693e (MD5)
Previous issue date: 1 | en |
| dcterms.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dcterms.subject | connexin, epidermis, GJB2, hemichannel, ichthyosis, skin disease | |
| dcterms.subject | Genetics | |
| dcterms.title | Inhibition of pathological connexin26 hemichannels implicated in keratitis-ichthyosis-deafness syndrome | |
| dcterms.type | Dissertation | |
