I am currently studying a class of intracellular ion channels know as ryanodine receptors (RyRs). In mammals, there are three RyR isoforms. RyR1 and RyR2 are the predominate isoforms in skeletal and cardiac muscle, respectively where they are the primary efflux pathway for the release of calcium from the sarcoplasmic reticulum to activate contraction. RyR3 has a wide tissue distribution and contributes to calcium regulation in a variety of cell types. RyRs are the largest known ion channel and are regulated by a multitude of endogenous effectors, including calcium, magnesium, adenine nucleotides, reactive oxygen and nitrogen species, accessory proteins such as calmodulin, FK506 binding protein, phosphatases, kinases, and even the L-type calcium channel, to name a few. Thus altering the sensitivity of the channel to regulators and/or changing the intracellular concentration of effector would impact RyR channel function, sarcoplasmic reticulum calcium release and modify muscle function. Therefore, an area of interest is the regulation of these channels by endogenous effectors; especially as it relates to altered contractile function associated with cardiac ischemia/reperfusion, skeletal muscle fatigue and aging.
Because of their central role in cellular calcium regulation, defects in RyR channels can lead to potentially fatal disorders. Mutations in RyR1 give rise to the pharmacogenetic disorder, malignant hyperthermia (MH). Recently RyR2 mutations have been identified in catecholaminergic polymorphic ventricular tachycardia (CPVT) and arrhythmogenic right ventricular dysplasia (ARVD) affected individuals. Interestingly, the mutations linked to CPVT and ARVD occur in the regions of RyR2 corresponding to the mutation-rich regions of RyR1 leading to MH. We are interested in determining the molecular mechanisms by which these mutations alter RyR channel function. No pathology has been linked to mutations in RyR3, yet.
We analyze channel function on multiples levels of organization. Sarcoplasmic reticulum vesicle [3H]ryanodine binding is used to examine large populations of channels. We incorporate channels into artificial lipid bilayers in order to record single channel currents and assess channel kinetics. Calcium release from permeabilized muscle fibers provides a method of examining RyR function in situ. My research has two long-range goals. The first is to understand how intracellular calcium is regulated and how alterations in the regulation effects cell function. The second goal is to understand the RyR regulatory sites that could potentially be exploited for the development of pharmacological compounds to treat disorders of cellular calcium regulation.
