Activation of a polyvalent cation-sensing receptor decreases magnesium transport via claudin-16

Biochim Biophys Acta. 2008 Jan;1778(1):283-90. doi: 10.1016/j.bbamem.2007.10.002. Epub 2007 Oct 12.

Abstract

Renal magnesium is mainly reabsorbed by a paracellular pathway in the thick ascending limb of Henle. The expression of claudin-16 increased magnesium transport in Madin-Darby canine kidney (MDCK) cells. Little is known about the regulatory mechanism of magnesium transport via claudin-16. Here we examined the effect of a polyvalent cation-sensing receptor (CaSR) on the intracellular distribution of and transport of magnesium by claudin-16. FLAG-tagged claudin-16 was stably expressed in MDCK cells using a Tet-OFF system. The activation of CaSR by magnesium, calcium, neomycin, and gadolinium did not affect the expression of FLAG-tagged claudin-16, CaSR, or ZO-1, a tight junctional scaffolding protein. These activators decreased the phosphoserine level of FLAG-tagged claudin-16 and the association of FLAG-tagged claudin-16 with ZO-1. The activation of CaSR induced a decrease in PKA activity. Immunofluorescence microscopy revealed that FLAG-tagged claudin-16 is distributed at the cell-cell border under unstimulated conditions, whereas it translocates to the intracellular compartment, mainly lysosome, with the activation of CaSR. In contrast, the distribution of ZO-1 was unaffected by the activation. The expression of FLAG-tagged claudin-16 increased transepithelial electrical resistance (TER) and transepithelial magnesium transport without affecting FITC-dextran (MW 4000) flux. The activation of CaSR decreased TER and magnesium transport, which were recovered by co-treatment with dibutyryl cAMP, a membrane-permeable cAMP analogue. Taken together, CaSR activation may decrease PKA activity, resulting in a decrease in phosphorylated claudin-16, the translocation of claudin-16 to lysosome and a decrease in magnesium reabsorption.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Bucladesine / pharmacology
  • Cell Line
  • Claudins
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Dogs
  • Electric Impedance
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Magnesium / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Phosphorylation / drug effects
  • Protein Transport / drug effects
  • Receptors, Calcium-Sensing / agonists
  • Receptors, Calcium-Sensing / metabolism*
  • Tetracycline
  • Tight Junctions / drug effects
  • Tight Junctions / metabolism

Substances

  • Claudins
  • Membrane Proteins
  • Receptors, Calcium-Sensing
  • claudin 16
  • Bucladesine
  • Cyclic AMP-Dependent Protein Kinases
  • Tetracycline
  • Magnesium