0000000000114127
AUTHOR
Clemens Gillen
The cAMP Pathway Sensitizes VR1 Expressed in Oocytes from <i>Xenopus laevis</i> and in CHO Cells
The vanilloid receptor 1 (VR1) is a heat-activated cation channel which also responds to capsaicin and other chemical stimuli. Protein kinase C has a stimulatory effect on VR1 activity, either alone or after activation with capsaicin. The influence of the cAMP-signaling pathway on the effects of capsaicin is controversial. To clarify this, the actions of capsaicin and the modulatory effects of forskolin, pCPT-cAMP, and isobutylmethylxanthine were studied in <i>Xenopus laevis</i> oocytes expressing rat VR1 and in CHO cells expressing human VR1. Capsaicin activated the VR1 channel and increased the intracellular calcium concentration. The effects of capsaicin were enhanced by fors…
Proton conductance of human transient receptor potential-vanilloid type-1 expressed in oocytes of Xenopus laevis and in Chinese hamster ovary cells.
Transient receptor potential-vanilloid type-1 (TRPV1) is a ligand-gated cation channel with preference for divalent cations, especially Ca(2+) (sequence of conductances: Ca(2+)Mg(2+)Na(+) approximately/= K(+) approximately/= Cs(+)). In the present study, the two-electrode voltage-clamp technique was used on oocytes of Xenopus laevis expressing TRPV1 to evaluate whether human TRPV1 also conducts protons. In medium devoid of K(+), Na(+), Mg(2+), and Ca(2+), capsaicin 1 microM induced a significant inward current (62% of the current in physiological medium). The effects of capsaicin were abolished in the presence of capsazepine 3 microM. The capsaicin-induced currents in medium devoid of Na(+)…
Activation by Acidic pH of CLC-7 Expressed in Oocytes from Xenopus laevis
ClC chloride channels are important in diverse physiological functions such as transepithelial transport, cell volume regulation, excitability, and acidification of intracellular organelles. We have investigated the expression of CLC-7 in oocytes from Xenopus laevis with the two electrode voltage clamp technique and Western blot analysis. Using a specific antibody against CLC-7, we found an approximately 80 kDa protein in oocytes, previously injected with CLC-7-cRNA. In voltage clamp experiments on ClC-7-cRNA-injected oocytes, no current changes were detected at normal pH (7.4). However, acidification of the Ringer solution to pH values between 6 and 4 revealed strong currents which reverse…