title: Polycystin-2 expression and function in adult mouse lacrimal acinar cells.
abstract: OBJECTIVE
  Lacrimal glands regulate the production and secretion of tear fluid. Dysfunction of lacrimal gland acinar cells can ultimately result in ocular surface disorders, such as dry eye disease. Ca(2+) homeostasis is tightly regulated in the cellular environment, and secretion from the acinar cells of the lacrimal gland is regulated by both cholinergic and adrenergic stimuli, which both result in changes in the cytosolic Ca(2+) concentration. We have previously described the detailed intracellular distribution of inositol-1,4,5-trisphosphate receptors (IP(3)Rs), and ryanodine receptors (RyRs) in lacrimal acinar cells, however, little is known regarding the expression and distribution of the third major class of intracellular Ca(2+) release channels, transient receptor potential polycystin family (TRPP) channels.
  
  
  METHODS
  Studies were performed in adult lacrimal gland tissue of Swiss-Webster mice. Expression, localization, and intracellular distribution of TRPP Ca(2+) channels were investigated using immunocytochemistry, immunohistochemistry, and electron microscopy. The biophysical properties of single polycystin-2 channels were investigated using a planar lipid bilayer electrophysiology system.
  
  
  RESULTS
  All channel-forming isoforms of TRPP channels (polycystin-2, polycystin-L, and polycystin-2L2) were expressed in adult mouse lacrimal gland. Subcellular analysis of immunogold labeling revealed strongest polycystin-2 expression on the membranes of the endoplasmic reticulum, Golgi, and nucleus. Biophysical properties of lacrimal gland polycystin-2 channels were similar to those described for other tissues.
  
  
  CONCLUSIONS
  The expression of TRPP channels in lacrimal acinar cells suggests a functional role of the proteins in the regulation of lacrimal fluid secretion under physiological and disease conditions, and provides the basis for future studies focusing on physiology and pharmacology.
authors.affiliation: Vision Research Center, University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri 64108, USA. kajas@umkc.edu
authors.forename: Simon
authors.initials: S
authors.lastname: Kaja
authors.forename: Jill D
authors.initials: JD
authors.lastname: Hilgenberg
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Rybalchenko
authors.forename: Wanda E
authors.initials: WE
authors.lastname: Medina-Ortiz
authors.forename: Elaine V
authors.initials: EV
authors.lastname: Gregg
authors.forename: Peter
authors.initials: P
authors.lastname: Koulen
mesh_terms: D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000502:physiology / Q000648:ultrastructure; D005089:Exocytosis / Q000502:physiology; D006056:Golgi Apparatus / Q000502:physiology / Q000648:ultrastructure; D007765:Lacrimal Apparatus / Q000378:metabolism* / Q000648:ultrastructure*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008854:Microscopy, Electron; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D050396:TRPP Cation Channels / Q000378:metabolism / Q000502:physiology*; D013666:Tears / Q000378:metabolism*
chemical_list: D002118:Calcium; D015220:Calcium Channels; D011956:Receptors, Cell Surface; D050396:TRPP Cation Channels; C486487:Pkd2l1 protein, mouse