PKP4 and neoplasm: FLCN has been shown to bind FNIP1, FNIP2, the Rag GTPases A and C/D, GABARAP and plakophilin-4 (refs 11, 12, 13, 14, 15, 16, 17, 18), but the biological significance of each of these interactions with regards to the tumour suppressor function of FLCN is under investigation.