Tuning of Calcium Signaling Pathways by Calmodulin: The Case of Cav1.3 Channels and Calcineurin

CaV1.3;Calmodulin;IQ domain;RNA-editing;FRET-based sensors;Calcineurin;NFAT;Biomedical Engineering

Bazzazi, HojjatLiu, Jun O. ;

Johns Hopkins University

关键词: CaV1.3;    Calmodulin;    IQ domain;    RNA-editing;    FRET-based sensors;    Calcineurin;    NFAT;    Biomedical Engineering;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/39308/HBazzaziThesis.doc?sequence=2&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

The modulation of voltage dependent calcium channels (CaV) by CaM has emerged as an important paradigm for understanding general CaM modulatory processes in biology. The prevailitng idea for CaM regulation of CaV channels has been the IQ-centric hypothesis. By combining scanning alanine mutagenesis and FRET 2-hybrid binding assays, the IQ-centric model is challenged. An alternative model whereby CaM departs from the IQ domain is described. By applying the same methodology to naturally occurring RNA edited variants of CaV1.3 channels, a surprising role for apoCaM modulation of CDI is discovered. This apoCaM modulation is then generalized to support a mechanism of tuning of calcium flux into brain cells via ambient fluctuations in CaM. The tuning mechanism is positioned for more general study by developing a novel genetically encoded sensor of calcineurin (CN) activation, CN being the dominant CaM-activated phosphatase throughout biology. By deploying the sensor in neonatal and acutely isolated adult cardiac myocytes, it is observed that CN is capable of being activated in response to single twitch calcium transients in neonatal but not in adult myocytes. The underlying mechanism for the differential CN activation in neonatal and adult myocytes is investigated with a mathematical model capable of fitting the cardiomyocyte sensor data at all experimentally investigated pacing frequencies (0.1Hz-1Hz). Our experimentally-based mathematical model identified free CaM concentration as the main parameter responsible for determining the amplitude and kinetics of CN response in neonatal and adult cardiomyocytes. The tuning conjecture of CaM for the function of both CaV1.3 and CN looms as a potentially central feature of Ca2+ signaling in brain and heart.