LIP1 is a protein found in eukaryotes. It represents the N-terminus of a leucine-rich-repeat protein that is implicated in Peutz-Jeghers syndrome. LIP1 interacts with the TGF-beta-regulated transcription factor SMAD4 to form a LKB1-LIP1-SMAD4 ternary complex. Mutations in SMAD4 lead to juvenile polyposis, suggesting a mechanistic link between these two diseases [1,2].

1: LIP1, a cytoplasmic protein functionally linked to the Peutz-Jeghers syndrome kinase LKB1. Smith DP, Rayter SI, Niederlander C, Spicer J, Jones CM, Ashworth A; Hum Mol Genet. 2001;10:2869-2877. PMID:11741830

2: Search for the second Peutz-Jeghers syndrome locus: exclusion of the STK13, PRKCG, KLK10, and PSCD2 genes on chromosome 19 and the STK11IP gene on chromosome 2. Buchet-Poyau K, Mehenni H, Radhakrishna U, Antonarakis SE; Cytogenet Genome Res. 2002;97:171-178. PMID:12438709