[Abstract Title]. - Society for Neuroscience

233. Nicotinic Aacetylcholine Receptors: Regulation and Function II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 233.16/C18
Topic: B.02.a. Nicotinic acetylcholine receptors in brain: Physiology and function
Support: NIH Grant DA13199
NIH Grant MH53631
NIH Grant DA06486
NIH Grant GM48677
Title: Fluorescent analogs of α-conotoxin ArIB: novel ligands for the study of α7 nicotinic
acetylcholine receptors
Authors: *A. J. HONE 1,2 , Y. XIAO 4 , S. CHRISTENSEN 3 , D. YOSHIKAMI 3,1 , J. M.
MCINTOSH 2,3,1 ;
1 Neurosci., 2 Psychiatry, 3 Biol., Univ. Utah, Salt Lake City, UT; 4 Pharmacol., Georgetown Univ.,
Washington DC, DC
Abstract: The α7 nicotinic acetylcholine receptor (nAChR) is widely distributed throughout the
central nervous system, and it has also been found on non-neuronal cells including lymphocytes
and macrophages. These receptors are thought to be homomeric pentamers with five ligand
binding sites; however, there is some evidence that they may also combine with additional
subunits to form heteromeric receptors. Although much is known about the localization and
function of α7 receptors within the central nervous system, much less is known about the role of
these receptors in the cellular processes of non-neuronal cell types. For example, historically α7
receptors have been thought of as ligand-gated ion channels that are highly permeable to Ca ++ ,
but recently it has been suggested that in lymphocytes, α7 subunits form receptors that may
modulate cellular function by a means not involving Ca ++ entry. The detection of α7 receptors on
lymphocytes and the elucidation of their function have been complicated by the lack of subtypeselective
ligands that can discriminate between α7 receptors and those that contain α1 or α9
subunits. To address this problem, we have labeled several analogs of α-conotoxin ArIB
(Whiteaker, et al., Biochemistry, 2007) with fluorescent probes to create novel ligands that
selectively bind α7 receptors. The pharmacology of these fluorescent ligands was assessed by
two electrode voltage clamp electrophysiology of Xenopus laevis oocytes expressing specific
subtypes of nAChRs. The fluorescent properties were assessed by fluorescence microscopy of
HEK293 cells stably transfected with the rat α7 subunit gene. The conotoxin analogs differed in
their biochemical properties and possessed unique pharmacological profiles. We hope to exploit
them to study α7 receptors, particularly in tissues where multiple nAChR subtypes are expressed.