PIP2 and PIP3 interact with N-terminus region of TRPM4 channel

- TRPM4 N- terminus channel contains binding site for potential regulatory molecules PIP2 and PIP3
- Basic R755 and R767 amino acids of TRPM4 N-terminal were determined to interact with the PIP2/PIP3 molecules directly
- TRPM4 fusion protein segments do not change its secondary structure content during complex formation with PIP2 or PIP3
- Molecular model of TRPM4 segment with PIP2 docking confirmed non-covalent binding mode

The transient receptor potential melastatin 4 (TRPM4) is a calcium-activated non-selective ion channel broadly expressed in a variety of tissues. Receptor has been identified as a crucial modulator of numerous calcium dependent mechanisms in the cell such as immune response, cardiac conduction, neurotransmission and insulin secretion. It is known that phosphoinositide lipids (PIPs) play a unique role in the regulation of TRP channel function. However the molecular mechanism of this process is still unknown. We characterized the binding site of PIP2 and its structural analogue PIP3 in the E733-W772 proximal region of the TRPM4 N-terminus via biophysical and molecular modeling methods. The specific positions R755 and R767 in this domain were identified as being important for interactions with PIP2/PIP3 ligands. Their mutations caused a partial loss of PIP2/PIP3 binding specificity. The interaction of PIP3 with TRPM4 channels has never been described before. These findings provide new insight into the ligand binding domains of the TRPM4 channel.