Authors
  Grando SA.  Zelickson BD.  Kist DA.  Weinshenker D.  Bigliardi PL. 
  Wendelschafer-Crabb G.  Kennedy WR.  Dahl MV.
Title
  Keratinocyte muscarinic acetylcholine receptors: immunolocalization and
  partial characterization.
Source
  Journal of Investigative Dermatology.  104(1):95-100, 1995 Jan.
Abstract
  We have reported previously that human keratinocytes synthesize and
  secrete acetylcholine and that muscarinic cholinergic drugs have effects
  on keratinocyte proliferation, adhesion, and migration. This study defines
  the location of muscarinic acetylcholine receptors in human epidermis and
  describes some pharmacologic and molecular properties of these receptors.
  Confocal microscopy employing the anti-muscarinic receptor monoclonal
  antibody M35 visualized the receptors in the intercellular areas of normal
  human epidermis. Using immunoelectron microscopy, the receptors appeared
  to be attached to the keratinocyte plasma membranes. Functional,
  high-density (Bmax = 8.3 nmol/2 x 10(6) cells) and high-affinity (Kd =
  21.5 nM) muscarinic receptors were demonstrated by saturable binding of
  the reversible radioligand [3H]quinuclidinyl benzilate to the surfaces of
  freshly isolated epidermal cells at 0 degrees C. Receptor proteins were
  separated by gel electrophoresis. An apparent isoelectric point of pH 4.3
  was determined in immunoblots of sodium-cholate-solubilized receptors
  separated on isoelectric-focusing gels. Three protein bands, two at
  approximately 60 kDa and one at 95 kDa, were visualized in immunoblots of
  membrane-bound or solubilized receptors separated by sodium
  dodecylsulfate-polyacrylamide gel electrophoresis. The covalent,
  irreversible ligand [3H]propylbenzilylcholine mustard confirmed these
  results. Thus, human keratinocytes express a heterogeneous population of
  muscarinic cholinergic receptors. Because human keratinocytes also express
  nicotinic cholinergic receptors, endogenously secreted acetylcholine may
  control different biologic processes in these cells by activating
  different types of their cholinergic receptors.