Two polyphosphatidylinositide metabolites control two K+ currents in a neuronal cell

Area of Science:

• Neuroscience
• Cellular Signaling
• Molecular Biology

Background:

• Phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) hydrolysis generates key intracellular messengers.
• Inositol 1,4,5-trisphosphate (InsP3) mobilizes intracellular Ca2+, while diacylglycerol (DG) activates protein kinase C.

Purpose of the Study:

• To investigate the sequential membrane conductance changes induced by bradykinin in NG108-15 cells.
• To elucidate the roles of InsP3 and DG in mediating these signaling events.

Main Methods:

• Utilized NG108-15 neuroblastoma-glioma hybrid cell line.
• Employed voltage-clamp recording techniques.
• Administered bradykinin and performed intracellular injections of Ca2+ and InsP3.

Main Results:

• Bradykinin rapidly hydrolyzes PtdIns(4,5)P2, increasing intracellular Ca2+ and causing membrane hyperpolarization followed by depolarization.
• Hyperpolarization is mediated by Ca2+-dependent K+ currents activated by InsP3.
• Depolarization results from the inhibition of the M-current by DG.

Conclusions:

• Demonstrates a dual, time-dependent role for InsP3 and DG in peptide-mediated neuronal signaling.
• Highlights the distinct contributions of InsP3 and DG to membrane potential changes.