Are soluble cytoplasmic components involved in demodulation?
Role of phosphorylation and cytosolic Ca2+ To assess the participation of protein phosphorylation in the demodulation of Som-mediated modulation, we used Na-OKA (1 µM added to the pipette solution) to prevent protein phosphatase activity (PP1 and PP2A) and to increase the general level of phosphorylation. If changes in phosphorylation were involved in this phenomenon, inhibiting phosphatases would be expected to prevent or at least modify demodulation. In the presence of OKA, the Som-mediated modulation (Fig. 4A, tr 10) was demodulated to -agonist-mediated modulation (tr 15) as described in Figure 1 above. These traces were selected from the diary plot of the percentage block of Ca2+ current inhibition illustrated in Figure 4B. The bar graph (Fig. 4C) summarizes the observations showing that demodulation in the presence of the phosphatase inhibitor was not different from that observed in control cells. View larger version (34K): [in this window] [in a new window] Figure 4. Changes in p
