TPC1 has been proposed to form a Ca2+ channel in the lysosomal membrane that is regulated by NAADP.21,27 We therefore probed the role of TPC1 in injury using mice lacking TPC1.33 TPC1 knockout mice have no obvious phenotype, but after subjecting them to experimental myocardial infarction they were revealed to be protected against cardiac ischaemia and reperfusion, with infarct sizes of 32 ± 4% of the area at risk, compared with 51 ± 5% of the area at risk in littermate wild-type controls (n = 4–5, P < 0.05; Figure 5B). Here, TPCN1 is linked to myocardial infarction.