Functional characteristics of TRPC4 channels expressed in HEK 293 cells.
The classical type of transient receptor potential (TRPC) channel is a molecular candidate for Ca(2+)-permeable cation channels in mammalian cells. Because TRPC4 and TRPC5 belong to the same subfamily of TRPC, they have been assumed to have the same physiological properties. However, we found that TRPC4 had its own functional characteristics different from those of TRPC5. TRPC4 channels had no constitutive activity and were activated by muscarinic stimulation only when a muscarinic receptor was co-expressed with TRPC4 in human embryonic kidney (HEK) cells. Endogenous muscarinic receptor appeared not to interact with TRPC4. TPRC4 activation by GTPgammaS was not desensitized. TPRC4 activation by GTPgammaS was not inhibited by either Rho kinase inhibitor or MLCK inhibitor. TRPC4 was sensitive to external pH with pK (a) of 7.3. Finally, TPRC4 activation by GTPgammaS was inhibited by the calmodulin inhibitor W-7. We conclude that TRPC4 and TRPC5 have different properties and their own physiological roles.
Sung
Tae Sik
TS
Center for Bio-Artificial Muscle and Department of Physiology, Seoul National University College of Medicine, Seoul, 110-799, Korea.
Kim
Min Ji
MJ
Hong
Soojin
S
Jeon
Jae-Pyo
JP
Kim
Byung Joo
BJ
Jeon
Ju-Hong
JH
Kim
Seon Jeong
SJ
So
Insuk
I
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D011976:Receptors, Muscarinic; D013449:Sulfonamides; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C491780:TRPC5 protein, human; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C017967:W 7; D017871:Calcium-Calmodulin-Dependent Protein Kinases