Regulates ciliary localization of the BBSome complex. Together with the BBSome complex, controls SMO ciliary trafficking and contributes to the sonic hedgehog (SHH) pathway regulation. May play a role in neurite outgrowth. May have tumor suppressor function. {ECO:0000269|PubMed:20233871, ECO:0000269|PubMed:22072986, ECO:0000269|PubMed:22510444}. This is the function of ENSG00000163818 (LZTFL1, leucine zipper transcription factor like 1).