title: Distinctive pharmacology and kinetics of cloned neuronal Ca2+ channels and their possible counterparts in mammalian CNS neurons.
abstract: This paper provides a brief overview of the diversity of voltage-gated Ca2+ channels and our recent work on neuronal Ca2+ channels with novel pharmacological and biophysical properties that distinguish them from L, N, P or T-type channels. The Ca2+ channel alpha 1 subunit known as alpha 1A or BI [Mori Y., Friedrich T., Kim M.-S., Mikami A., Nakai J., Ruth P., Bosse E., Hofmann F., Flockerzi V., Furuichi T., Mikoshiba K., Imoto K., Tanabe T. and Numa S. (1991) Nature 350, 398-402] is generally assumed to encode the P-type Ca2+ channel. However, we find that alpha 1A expressed in Xenopus oocytes differs from P-type channels in its kinetics of inactivation and its degree of sensitivity to block by the peptide toxins omega-Aga-IVA and omega-CTx-MVIIC [Sather W. A., Tanabe T., Zhang J.-F., Mori Y., Adams M. E. and Tsien R. W. (1993) Neuron 11, 291-303]. Thus, alpha 1A is capable of generating a Ca2+ channel with characteristics quite distinct from P-type channels. Doe-1, recently cloned from the forebrain of a marine ray, is another alpha 1 subunit which exemplifies a different branch of the Ca2+ channel family tree [Horne W. A., Ellinor P. T., Inman I., Zhou M., Tsien R. W. and Schwarz T. L. (1993) Proc. Natn. Acad. Sci. U.S.A. 90, 3787-3791]. When expressed in Xenopus oocytes, doe-1 forms a high voltage-activated (HVA) Ca2+ channel [Ellinor P. T., Zhang J.-F., Randall A. D., Zhou M., Schwarz T. L., Tsien R. W. and Horne W. (1993) Nature 363, 455-458]. It inactivates more rapidly than any previously expressed calcium channel and is not blocked by dihydropyridine antagonists or omega-Aga-IVA. Doe-1 current is reduced by omega-CTx-GVIA, but the inhibition is readily reversible and requires micromolar toxin, in contrast to this toxin's potent and irreversible block of N-type channels. Doe-1 shows considerable sensitivity to block by Ni2+ or Cd2+. We have identified components of Ca2+ channel current in rat cerebellar granule neurons with kinetic and pharmacological features similar to alpha 1A and doe-1 in oocytes [Randall A. D., Wendland B., Schweizer F., Miljanich G., Adams M. E. and Tsien R. W. (1993) Soc. Neurosci. Abstr. 19, 1478]. The doe-1-like component (R-type current) inactivates much more quickly than L, N or P-type channels, and also differs significantly in its pharmacology.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University Medical Center, CA 94305.
authors.forename: J F
authors.initials: JF
authors.lastname: Zhang
authors.forename: A D
authors.initials: AD
authors.lastname: Randall
authors.forename: P T
authors.initials: PT
authors.lastname: Ellinor
authors.forename: W A
authors.initials: WA
authors.lastname: Horne
authors.forename: W A
authors.initials: WA
authors.lastname: Sather
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
authors.forename: T L
authors.initials: TL
authors.lastname: Schwarz
authors.forename: R W
authors.initials: RW
authors.lastname: Tsien
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002999:Clone Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*
chemical_list: D015220:Calcium Channels