TRPM2 is a Ca²⁺-permeable ion channel which mediates susceptibility to cell death following activation by oxidative stress, TNF, or -amyloid peptide. We determined that TRPM2 is rapidly tyrosine phosphorylated after stimulation with H₂O₂ or TNF. Inhibition of tyrosine phosphorylation with tyrosine kinase inhibitors genistein or PP2 significantly reduced the increase in [Ca²⁺]_i observed after H₂O₂ or TNF treatment in TRPM2-expressing cells, suggesting that phosphorylation is important in TRPM2 activation. Utilizing a TransSignal PDZ Domain Array Blot to identify proteins which interact with TRPM2, we identified PTPL1 as a potential binding protein. PTPL1 is a widely expressed tyrosine phosphatase which has a role in cell survival. Immunoprecipitation and GST-pulldown assays confirmed that TRPM2 and PTPL1 interact. To examine the ability of PTPL1 to modulate TRPM2 phosphorylation or activation, PTPL1 was coexpressed with TRPM2 in HEK 293T cells. This resulted in significantly reduced TRPM2 tyrosine phosphorylation, and inhibited the rise in [Ca²⁺]_i and the loss of cell viability which follow H₂O₂ or TNF treatment. Consistent with this, reduction in endogenous PTPL1 expression with siRNA resulted in increased TRPM2 tyrosine phosphorylation, significantly greater rise in [Ca²⁺]_i, and enhanced susceptibility to H²O²-induced cell death. Endogenous TRPM2 and PTPL1 associated in U937-ecoR cells, confirming physiological relevance. These data demonstrate that tyrosine phosphorylation of TRPM2 is important in its activation and function, and that inhibition of TRPM2 tyrosine phosphorylation reduces Ca²⁺ influx and protects cell viability. They suggest that modulation of TRPM2 tyrosine phosphorylation is a mechanism through which PTPL1 may mediate resistance to cell death.