Store-depletion and hyperforin activate distinct types of Ca(2+)-conducting channels in cortical neurons.
Cortical neurons embryos (E13) from murine brain have a wide diversity of plasma membrane Ca(2+)-conducting channels. For instance, they express several types of transient receptor potential channels of C-type (TRPC) and hyperforin, a potent TRPC6-channel activator, controls the activity of TRPC6-like channels. In addition, E13 cortical neurons possess plasma membrane channels activated in response to the depletion of internal Ca(2+) pools. Since some TRPC channels seem to be involved in the activity of store-depletion-activated channels, we investigated whether hyperforin and the depletion of the Ca(2+) stores control similar or distinct Ca(2+) routes. Calcium imaging experiments performed with the fluorescent Ca(2+) indicator Fluo-4 showed that the TRPC3 channel blocker Pyr3 potently inhibits with an IC(50) of 0.5microM the entry of Ca(2+) triggered in response to the thapsigargin-dependent depletion of the Ca(2+) stores. On the other hand, Pyr3 does not block the hyperforin-sensitive Ca(2+) entry. In contrast to the hyperforin responses, the Ca(2+) entry through the store-depletion-activated channels is down-regulated by the competitive tyrosine kinase inhibitors genistein and PP2. In addition, the immunosuppressant FK506, known to modulate several classes of Ca(2+)-conducting channels, strongly attenuates the entry of Ca(2+) through the store-depletion-activated channels, leaving the hyperforin-sensitive responses unaffected. Hence, the Zn(2+) chelator TPEN markedly attenuated the hyperforin-sensitive responses without modifying the thapsigargin-dependent Ca(2+) signals. Pyr3-insensitive channels are key components of the hyperforin-sensitive channels, whereas the thapsigargin-dependent depletion of the Ca(2+) stores of the endoplasmic reticulum activates Pyr3-sensitive channels. Altogether, these data support the notion that hyperforin and the depletion of the Ca(2+) pools control distinct plasma membrane Ca(2+)-conducting channels. This report further illustrates that, at the beginning of the corticogenesis, immature cortical neurons express diverse functional Ca(2+) channels.
Gibon
Julien
J
UMR CNRS, Grenoble, France.
Tu
Peng
P
Bouron
Alexandre
A
D000814:Aniline Compounds / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D005456:Fluorescent Dyes / Q000737:chemistry / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D014966:Xanthenes / Q000737:chemistry / Q000494:pharmacology
D000814:Aniline Compounds; D001643:Bridged Bicyclo Compounds; D002121:Calcium Channel Blockers; D015220:Calcium Channels; C409648:Fluo 4; D005456:Fluorescent Dyes; D007166:Immunosuppressive Agents; D050052:TRPC Cation Channels; D013729:Terpenes; D014966:Xanthenes; D019284:Thapsigargin; D010696:Phloroglucinol; C001654:hyperforin; D002118:Calcium; D016559:Tacrolimus