Voltage-dependent calcium channels (VDCCs) serve two critical functions: the regulation of cellular excitability, and the regulation of Ca2+ entry. Ca2+ dysfunction accompanies adult disease progression such as in cardiac hypertrophy. Thus, it follows that the chronic regulation of voltage-dependent Ca2+ channel expression is critical to the function of the heart and skeletal muscle. The guiding hypothesis of this proposal is that the Ras-related GTPase Rem regulates Ca2+ channel activity in cardiac and skeletal muscle by the novel mechanism of interacting with the beta-subunits of voltage-gated Ca2+ channels to block their association with alpha1-subunits. We hypothesize that this inhibits channel activity by blocking trafficking of functional calcium channels to the plasma membrane. This hypothesis was motivated by the following pilot studies: 1) Rem is highly expressed in cardiac and skeletal muscle. 2) Rem binds to beta- subunits. 3) Over-expression of wild-type Rem inhibits ionic current expression in heterologous expression systems, and importantly, in primary ventricular myocytes. 4) T-type Ca 2+ channels do not require accessory subunits and Rem does not inhibit expression of currents through this family of channels. This suggests that Rem regulates Ca2+ channel activity in a beta-subunit-dependent fashion. 5) Rem-mediated regulation of CaV1 channels is not understood, but initial studies have defined a crucial role for the Rem C-terminal domain in this process. We propose three specific aims to elucidate the function of Rem as a regulator of voltage-dependent Ca2+ channel activity.
Specific Aim 1 will identify the amino acid sequences in Rem and the Ca2+ channel beta- subunit important for their interaction.
Specific Aim 2 will determine if formation of the Rem:beta-subunit complex is regulated in vivo by 14-3-3 protein binding and GTPase activity. Studies will also examine the role of the C-terminal domain in Rem-mediated Ca2+ channel regulation.
Specific Aim 3 will characterize the mechanism of Rem-mediated regulation of alpha1 channel activity by examining Rem effects on the association of alpha1 and beta-subunits and channel trafficking. These studies will advance knowledge by elucidating a new mechanism for controlling chronic Ca2+ channel activity as well as a novel mechanism for achieving cross talk between Ras-related GTPases and electrical signaling pathways. This knowledge could aid understanding of the regulation of voltage-dependent Ca2+ channels in both normal and disease states.
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| Manning, Janet R; Withers, Catherine N; Levitan, Bryana et al. (2015) Loss of Rad-GTPase produces a novel adaptive cardiac phenotype resistant to systolic decline with aging. Am J Physiol Heart Circ Physiol 309:H1336-45 |
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| Gunton, Jenny E; Sisavanh, Mary; Stokes, Rebecca A et al. (2012) Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling. PLoS One 7:e39462 |
| Magyar, Janos; Kiper, Carmen E; Sievert, Gail et al. (2012) Rem-GTPase regulates cardiac myocyte L-type calcium current. Channels (Austin) 6:166-73 |
| Shi, Geng-Xian; Andres, Douglas A; Cai, Weikang (2011) Ras family small GTPase-mediated neuroprotective signaling in stroke. Cent Nerv Syst Agents Med Chem 11:114-37 |
| Pang, Chunyan; Crump, Shawn M; Jin, Ling et al. (2010) Rem GTPase interacts with the proximal CaV1.2 C-terminus and modulates calcium-dependent channel inactivation. Channels (Austin) 4:192-202 |
| Shi, Geng-Xian; Jin, Ling; Andres, Douglas A (2010) Src-dependent TrkA transactivation is required for pituitary adenylate cyclase-activating polypeptide 38-mediated Rit activation and neuronal differentiation. Mol Biol Cell 21:1597-608 |
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