Ion Channel Lateral Diffusion Reveals the Maturation Process of the Neuronal Actin Cytoskeleton.

Abstract

mall-conductance calcium-acti v ated potassium (SK) channels r e v olta ge-inde pendent K + channels that acti v ate in r esponse o a rise in cytoplasmic Ca 2 + 1 . In neurons, they are, therefore, b le to r educe Ca 2 + entr y in spines and dendrites, limiting proonged depolarization. SK channels can also be found in the oma and in axons, where they likely contribute to spike freuency adaptation. Gu and colleagues used single-particle tr ac kng 2 of SK channels in different areas of pyramidal hippocamal neurons in cultures of different ages. The diffusion coefcient of SK channels was determined along the maturation rocess of the neuronal culture using biotinylated apamin and tr e ptavidin-conjugated quantum dots to label the channels in ombination with total internal reflection microscopy. At the ame time, actin cytoskeleton integrity was manipulated pharacologically to investigate its impact on the diffusion velocity f SK channels. The approach allowed tracking the diffusion of he channel in different compartments, which served as a proxy o determine the stability of actin cytoskeletal structures. Since ta b le actin filaments limited the distribution of SK channels, it as possib le to infer how structured the actin cytoskeleton was long the maturation pr ocess. Importantl y, the submembrane ctin cytoskeleton is incr easingl y r egarded as a crucial factor for odulating the activity of ion channels and transporters at the lasma membrane (see Morache vska ya and Sudarikova 3 ). Neuronal function critically depends on the cytoar c hitecture f the neuron. The cytoskeleton plays a critical role in mainaining the proper neural computation that goes far beyond er e mechanical sta bility and shape maintenance. Specialized tructures crucial for neurotransmission, such as the node of anvier, the axon initial segment (AIS), or synaptic terminals, are