Targeting voltage-gated ion channels to axons Flashcards
Lai, H. C., & Jan, L. Y. (2006). The distribution and targeting of neuronal voltage-gated ion channels. Nature reviews. Neuroscience, 7(7), 548–562. https://doi.org/10.1038/nrn1938
What are Nav channels responsible for in axons?
In axons, Nav channels are responsible for action potential initiation at the AIS and the nodes of Ranvier, action potential propagation along the unmyelinated axon, and action potential back-propagation in dendrites.
What is the general distribution of Nav channels?
The principal Nav channels in the AIS and nodes of Ranvier are Nav1.2 and Nav1.6, and their distribution can change during development in a myelin-dependent manner.
Nav1.1, Nav1.2, Nav1.3 and Nav1.6
are expressed mainly in the CNS.
Nav1.4 and Nav1.5 are
found in the cardiac and skeletal muscle systems.
Nav1.7, Nav1.8 and Nav1.9 are found in the PNS, although there are exceptions (for example, Nav1.2 and Nav1.6 are found at the nodes of Ranvier in the sciatic nerve.
What are Kv1 channels responsible for in axons and synaptic terminals?
They help to control action potential propagation and neurotransmitter release.
What are KCNQ channels responsible for?
The Kv7 (KCNQ) channels are slow
delayed rectifiers that activate at sub-threshold levels to maintain the resting potential and reduce excitability.
KCNQ2 is localized to the AIS and nodes of Ranvier in the CNS and PNS and is co-localized with KCNQ3 at only some of these locations.
KCNQ2/3 channels underlie the M-current (IM), which is activated at sub-threshold potentials and modulated by G-proteins. Mutations in these channels cause myokymia and benign familial neonatal convulsions (BFNCs), underscoring their importance in controlling excitability.
Moreover, electrophysiological studies show that KCNQ channels in premyelinated fibres of the optic nerve control excitability, a role similar to that of Kv1 channels at the nodes of the sciatic nerve during development.
What are Kv3 channels responsible for?
There are four Kv3 genes, Kv3.1 to Kv3.4, which have multiple splice forms. Kv3.1 and Kv3.2 display delayed rectifier currents, whereas Kv3.3 and Kv3.4 give rise to A-type currents.
Typically found in fast-spiking central neurons, Kv3 channels might comprise different combinations of Kv3-family members, and are important for action potential repolarization and sustaining high-frequency firing.
