Calcium receptor message, expression and function decrease in differentiating keratinocytes.
Calcium-sensing receptor (CaSR) expression and function were studied in proliferating and differentiating cultured human gingival keratinocytes (HGKs). CaSR mRNA and protein were present in proliferating HGKs cultured in 0.03 mM [Ca(2+)] and decreased in cells induced to differentiate by culturing in 1.2 mM [Ca(2+)] for 2 days. CaSR protein was also detected in gingival tissue. Exposure to 10 mM extracellular [Ca(2+)] activated two sequential whole-cell currents. The first was a small, transient calcium release activated calcium current I(CRAC)-like current with an inwardly rectifying I-V curve. The second current was larger with a linear I-V curve. Both currents were significantly decreased in differentiating cells. Neither neomycin nor gadolinium induced changes in whole cell currents nor in intracellular [Ca(2+)], but neomycin inhibited the late large current. Extracellular Ca(2+) increased intracellular [Ca(2+)] of proliferating HGKs in a dose-dependent fashion. Comparison of the time-courses of the whole-cell currents and the intracellular [Ca(2+)] responses indicated both induced currents supported a Ca(2+) influx. Extracellular [Mg(2+)] changes did not affect intracellular [Ca(2+)]. La(3+) and 2-APB inhibited the whole cell current and intracellular [Ca(2+)] changes. The results indicate that the CaSR signaling response likely plays a major role in initiating Ca(2+) induced differentiation responses in HGKs.
Fatherazi
Sahba
S
Department of Oral Biology, School of Dentistry, University of Washington, Seattle, WA 98195, USA.
Belton
Carol M
CM
Cai
Shiwei
S
Zarif
Shukriya
S
Goodwin
Paul C
PC
Lamont
Richard J
RJ
Izutsu
Kenneth T
KT
D015153:Blotting, Western; D020013:Calcium Signaling / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D016257:Fura-2 / Q000031:analogs & derivatives*; D005682:Gadolinium / Q000494:pharmacology; D005881:Gingiva / Q000166:cytology; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology; D008856:Microscopy, Fluorescence; D009355:Neomycin / Q000819:agonists; D018408:Patch-Clamp Techniques; D011500:Protein Synthesis Inhibitors / Q000819:agonists; D012313:RNA / Q000302:isolation & purification; D044169:Receptors, Calcium-Sensing / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D008565:Membrane Proteins; D011500:Protein Synthesis Inhibitors; D044169:Receptors, Calcium-Sensing; C049925:fura-2-am; D012313:RNA; D005682:Gadolinium; D009355:Neomycin; D016257:Fura-2