Final answer:
The question does not directly address the auxiliary subunits on calcium channels, but discusses the role of calcium in cardiac muscle function and the importance of AMPA and NMDA receptors in neuronal signalling, which are indirectly related to calcium channels.
Step-by-step explanation:
The auxiliary subunits on calcium channels are essential components that modify the biophysical properties of these channels. In the context of neuronal signaling, calcium channels contribute to vital functions such as muscle contraction, neurotransmitter release, and gene expression. While the information provided does not explicitly describe the auxiliary subunits on calcium channels, it does mention the role of calcium ions in cardiac muscle physiology and AMPA and NMDA receptors in the brain.
AMPA receptors are typically composed of GluA1 through GluA4 subunits and are important in processes like long-term potentiation. NMDA receptors, which are assembled from NR1, NR2, and NR3 subunits, have slow gating kinetics and are highly permeable to both calcium and sodium, initiating calcium-mediated biochemical cascades. Importantly, AMPA receptors lacking the GluA2 subunit are calcium-permeable and play a significant role in synaptic plasticity. The modification of AMPA receptors through the action of the enzyme Adenosine deaminase acting on RNA 2 (ADAR2), which edits the RNA to include a GluA2 subunit, results in the formation of calcium-impermeable receptors. This enzymatic action is a potential target for reducing excitotoxicity in neurodegenerative diseases.