The dramatic inhibition of TRPM8 channel activity by scPPX1 led us to investigate whether polyP is associated with the protein. For our studies of the biochemical and biophysical properties of TRPM8, we purified the protein from the
HEK-293 cell line stably expressing TRPM8. Plasma membranes were isolated by differential centrifugation with subsequent extraction of the TRPM8 protein with 1% Nonidet and 0.5% dodecylmaltoside (DDM) (see materials and methods).