Transient receptor potential channel TRPM8 agonists stimulate calcium influx and neurotensin secretion in neuroendocrine tumor cells.
TRPM8 is a member of the melastatin-type transient receptor potential ion channel family. Activation by cold or by agonists (menthol, icilin) induces a transient rise in intracellular free calcium concentration ([Ca(2+)](i)). Our previous study demonstrated that Ca(2+)-permeable cation channels play a role in IGF-1-induced secretion of chromogranin A in human neuroendocrine tumor (NET) cell line BON [Mergler et al.: Neuroendocrinology 2006;82:87-102]. Here, we extend our earlier study by investigating the expression of TRPM8 and characterizing its impact on [Ca(2+)](i) and the secretion of neurotensin (NT). We identified TRPM8 expression in NET BON cells by RT-PCR, Western blotting and immunofluorescence staining. Icilin increased [Ca(2+)](i) in TRPM8-transfected human embryonic kidney cells (HEK293) but not in mock-transfected cells. Icilin and menthol induced Ca(2+) transients in BON cells as well as in primary NET cell cultures of two different pancreatic NETs as detected by single cell fluorescence imaging. Icilin increased non-selective cation channel currents in BON cells as detected by patch-clamp recordings. This activation was associated with increased NT secretion. Taken together, this study demonstrates for the first time the expression TRPM8 in NET cells and its role in regulating [Ca(2+)](i) and NT secretion. The regulation of NT secretion in NETs by TRPM8 may have a potential clinical implication in diagnosis or therapy.
Mergler
Stefan
S
Department of Internal Medicine, Division of Hepatology and Gastroenterology, Charité - Universitatsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany. stefan.mergler@charite.de
Strowski
Mathias Z
MZ
Kaiser
Simone
S
Plath
Thomas
T
Giesecke
Yvonne
Y
Neumann
Marleen
M
Hosokawa
Hiroshi
H
Kobayashi
Shigeo
S
Langrehr
Jan
J
Neuhaus
Peter
P
Plöckinger
Ursula
U
Wiedenmann
Bertram
B
Grötzinger
Carsten
C
D002118:Calcium / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008610:Menthol / Q000494:pharmacology*; D008954:Models, Biological; D018358:Neuroendocrine Tumors / Q000473:pathology*; D009496:Neurotensin / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D011744:Pyrimidinones / Q000494:pharmacology*; D050053:TRPM Cation Channels / Q000819:agonists* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011744:Pyrimidinones; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D008610:Menthol; D009496:Neurotensin; C490483:icilin; D002118:Calcium