Glucocorticoids (GCs) are administered to neonates and to pregnant mothers for the treatment of complications arising from premature birth and for congenital adrenal hyperplasia; however, antenatal exposure to GCs may trigger adverse neurological side effects due in part to reduced neural progenitor cell (NPC) proliferation. While many established cell cycle regulators impact NPC proliferation, other molecules also influence proliferation. An example is the gap junction protein connexin 43 (Cx43), although its precise role and mechanism of regulation remain unresolved. Gap junction intercellular communication (GJIC) is influenced by GCs in some cells, but such hormone effects and resulting functional consequences have not been examined in coupled stem cells. We found that both continuous and transient exposure of embryonic (E14.5) mouse neurosphere cultures to the glucocorticoid dexamethasone (DEX) limits proliferation of coupled NPCs, which is manifested by both a reduction in S phase progression and enhanced cell cycle exit. A short (i.e. 1hr) DEX treatment also reduced GJIC as measured by live cell fluorescence recovery after photobleaching (FRAP). GC effects on GJIC in NPCs are transcription-independent and mediated through plasma membrane glucocorticoid receptors (GRs). This non-classical pathway appears to operate through lipid-raft associated GRs through a site-specific, MAPK-dependent phosphorylation of Cx43, which is linked to GR via caveolin-1 and c-src. These effects were absent in caveolin-1 knockout NPCs indicating that caveolin-1 is an essential component for this signaling pathway. As transient pharmacologic inhibition of GJIC triggers reduced S phase progression but not enhanced cell cycle exit, the non-classical GR signaling pathway may operate via distinct downstream effectors to alter the proliferative capacity of NPCs.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-07132011-120711 |
| Date | 30 September 2011 |
| Creators | Samarasinghe, Ranmal Aloka |
| Contributors | Stephen Hammes, Guillermo Romero, Elias Aizenman, Donald DeFranco, Paula Monaghan-Nichols, Charleen Chu, Sarah Berman |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-07132011-120711/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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