Posttranslational regulation of Ca2+-activated K+ currents by a target-derived factor in developing parasympathetic neurons

Macroscopic /(K[Ca) is not expressed at normal levels in chick ciliary ganglion (CG) neurons prior to synapse formation with target tissues, or in neurons developing in vitro or in situ in the absence of target tissues. Here, two chick CG s/o partial cDNAs encoding /(K[Ca) channels were isolated, cloned, and sequenced. Both s/o transcripts were readily detected in developing Co neurons prior to or in the absence of target tissue interactions. When Co neurons developed in vitro in the presence of target tissue (iris) extracts, a normal whole-cell /(K[Ca) was expressed. These effects did not require protein synthesis, and the activity was detectable throughout the stages of synapse formation in the iris. The active component has an apparent molecular weight of 40-60 kDa.