Protein-protein adapter that drives transport of G protein- coupled receptors into primary cilia by mediating association between the intraflagellar transport complex A (IFT-A) and G protein-coupled receptors FFAR4, GPR45 and GPR161 (PubMed:11375483, PubMed:20889716, PubMed:31761534, PubMed:36775821). Acts as a negative regulator of the Shh signaling by promoting trafficking of GPR161 to cilia (PubMed:20889716, PubMed:36775821). During adipogenesis, regulates ciliary trafficking of FFAR4 in preadipocytes (PubMed:31761534). Promotes transport of GPR45 into primary cilia of neurons in paraventricular nucleus (PVN) of the hypothalamus (By similarity). Binds to phosphorylated inositide (phosphoinositide) lipids; both IFT- A- and phosphoinositide-binding properties are required to regulate ciliary G protein-coupled receptor trafficking (PubMed:11375483, PubMed:20889716). Besides its role in cilium localization, acts as a regulator of AMP-activated protein kinase (AMPK) activity in response to calorie restriction: binds lithocholic acid, a metabolite generated in response to calorie restriction, promoting TULP3 ability to activate SIRT1, which then deacetylates the ATP6V1E1 subunit of the V-ATPase complex, leading to (1) V-ATPase complex inhibition on lysosomes and (2) AMPK activation via the AXIN1-STK11/LKB1 axis (By similarity). {ECO:0000250|UniProtKB:O88413, ECO:0000269|PubMed:11375483, ECO:0000269|PubMed:20889716, ECO:0000269|PubMed:31761534, ECO:0000269|PubMed:36775821}. This is the function of TULP3 (TUB like protein 3, ENSG00000078246).