Copper-induced early responses involve the activation of Transient Receptor Potential (TRP) channels, release of amino acids, serotonin and adrenalin, and activation of homologs of glutamate, adrenalin and serotonin receptors in the marine alga Ulva compressa

Abstract

It has been previously shown that U. compressa cultivated with 10μM copper showed the activation of Transient Receptor Potential (TRP) channels at 4, 8 and 13min allowing copper ions entry and transient depolarizations. Here, the alga was incubated with copper and with inhibitors of human TRP channels that were incorporated just after copper addition (time 0), and after 1 and 2min of copper exposure, and membrane depolarizations were detected at 4, 8 and 13min. Copper induced the activation of a TRP A1/C5/M8 at time 0, a TRP A1/C4/M8/V1 after 1min, and a TRP A1/C5/M8, after 2min of copper exposure. In addition, EGTA, a specific calcium chelator, did not inhibit depolarization events when added at time 0, and after 1 and 2min, whereas bathocuproine, a specific copper chelator, inhibited transient depolarizations at 4, 8 and 13min. In addition, inhibitors of human GluR of NMDA type, added at time 0, and GluR of AMPA/KA types, added after 1 and 2min as well as inhibitors of serotonin and adrenalin receptors added after 2min inhibited depolarizations at 4, 8 and 13min. Furthermore, amino acids, serotonin and adrenalin were release to culture medium in response to copper excess. Thus, copper ions induces the activation of TRP channels allowing extracellular copper ions entry leading to transient depolarizations, release of aminoacids, serotonin, and adrenalin, and activation of homologs of glutamate, adrenalin and serotonin receptors which are involved in the activation of TRPs and depolarizations observed at 4, 8 and 12min of copper exposure.