Members of the transient receptor potential (TRP) channel family are highly diverse ion channels that were first discovered in Drosophila photoreceptors, where they are the dominant light-sensitive channel. TRPs are activated by a signalling cascade that includes phospholipase C (PLC), which hydrolyses phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] in the microvillar membrane. The TRP channel in Drosophila is highly selective for Ca2+ and responsible for extensive Ca2+ influx during the response to light. In trp mutant flies this Ca2+ influx is reduced and results in retinal degeneration. It had previously been suggested that this is because of the resulting defects in Ca2+-dependent steps of the visual pigment cycle, which lead to the accumulation of toxic hyperphosphorylated metarhodopsin–arrestin (MPP–Arr2). On page 1247, Roger Hardie and colleagues explore an alternative hypothesis, namely that degeneration in trp mutants is due to failure of Ca2+-dependent inhibition of PLC, resulting in depletion of PtdIns(4,5)P2. They find that retinal degeneration is not rescued when accumulation of MPP–Arr2 is prevented but rescued when PLC is mutated, and that it correlates closely with the extent of PtdIns(4,5)P2 depletion. Furthermore, the authors demonstrate that depletion of PtdIns(4,5)P2 leads to the dephosphorylation of the cytoskeletal component moesin, the subsequent depolymerisation of actin and the disintegration of the microvillar membrane, thus providing new insights into the molecular mechanism of degeneration.