sentences:  These opposing effects of "FLCN" deficiency on the mTOR pathway have led to the hypothesis that FLCN regulation of mTOR activity may be context or cell-type dependent.Resolution of the crystal structure of the FLCN carboxy-terminal protein domain revealed a structural similarity to the differentially expressed in normal cells and neoplasia (DENN) domain of DENN1B suggesting that they are distantly related proteins.The DENN domain family of proteins are guanine nucleotide exchange factors (GEFs) for Rab proteins, members of the Ras superfamily of G proteins that are involved in vesicular transport suggesting that FLCN may have a similar function.