Heart disease is the number one cause of death in the United States. There are many forms of heart disease including heart failure and arrhythmias. One underlying theme in heart disease and many other diseases is disrupted Ca2+ homeostasis. Calcium is a charge carrier and universal mediator of diverse cellular processes. In cardiac myocytes, these processes include excitation-contraction coupling, gene transcription and apoptosis.
Ca2+ enters cardiac myocytes through L-type Ca2+ channels (LTCC) where it activates signaling molecules such as the multifunctional Ca2+/calmodulin dependent protein kinase II (CaMKII). CaMKII is one of many specialized proteins poised to respond to Ca2+ signaling in cardiac myocytes. Accumulating evidence links cardiac CaMKII activity to normal physiological regulation of several heart functions and to multiple pathological conditions.
CaMKII is associated with cardiac LTCC complexes and increases channel open probability (PO) to dynamically increase Ca2+ current (ICa) and augment cellular Ca2+ signaling by a process called facilitation. I found that activated CaMKII binds to the LTCC b2a subunit close to a preferred CaMKII phosphorylation site, Thr498 and colocalizes with b2a in cardiomyocytes. Mutation of Thr498 to Ala (T498A) in b2a prevents CaMKII-mediated increases in the PO of recombinant LTCCs. Moreover, expression of b2a (T498A) in adult cardiomyocytes ablates CaMKII-mediated ICa facilitation, demonstrating that phosphorylation of b2a at Thr498 modulates native Ca2+ channels.
In addition, I showed that binding requires CaMKII activation but phosphorylation at Thr498 inhibits binding. The b2a subunit also modulates CaMKII activity and enhances CaMKII autophosphorylation at a site other than Thr287 or Thr305/306. Analysis of the primary sequences of the four b isoforms reveal that the CaMKII binding/regulatory site is conserved in b1b but not in b3 nor b4 and CaMKII was shown to interact with b1b in a similar manner as b2a.
Taken together these findings reveal a novel molecular mechanism for dynamic targeting of CaMKII to LTCCs and facilitating ICa that may modulate Ca2+ entry in diverse cell types co-expressing CaMKII and the b2a subunit. Future work based on these findings may identify a potential pharmacological target for the treatment of heart disease or other pathological conditions involving disrupted Ca2+ homeostasis.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-11132006-143811 |
| Date | 13 November 2006 |
| Creators | Grueter, Chad Eric |
| Contributors | Danny Winder, Kevin Currie, Daniel Liebler, John Exton, Jackie Corbin |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-11132006-143811/ |
| Rights | unrestricted, 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 Vanderbilt University 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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