YIPF6

YIPF6 is a five-transmembrane Golgi-resident protein that functions as a regulator of ER-to-Golgi cargo sorting and secretory pathway homeostasis, with a defining requirement in intestinal epithelial secretion (PMID:22802641, PMID:27999994). Loss of YIPF6 in mice causes defective formation and secretion of large secretory granules from Paneth and goblet cells, producing spontaneous intestinal inflammation (PMID:22802641). The protein spans the Golgi stack across both cis and trans compartments, with a cytosol-facing N-terminus and a lumen-facing C-terminus, and its depletion alters Golgi morphology (PMID:27999994). YIPF6 assembles into a stable complex with YIPF1 and YIPF2 at the medial/trans-Golgi and TGN, and is required for the stable expression and Golgi localization of these partners (PMID:28286305). It also interacts with the trans-Golgi protein TVP23B, and loss of either protein depletes glycosylation enzymes from the colonocyte Golgi proteome, linking YIPF6 to glycosylation enzyme trafficking and intestinal homeostasis (PMID:37339972). In a distinct secretory role, YIPF6 binds FGF21 in the ER and controls its packaging into COPII vesicles, thereby limiting FGF21 secretion; its loss raises plasma FGF21 and confers resistance to diet-induced obesity (PMID:31289229). YIPF6 additionally modulates extracellular vesicle secretion in prostate cancer cells (PMID:28144969).

1. 2006 Medium

   Establishing where the YIPF6 ortholog acts placed the protein in the late Golgi/endosomal maintenance machinery rather than the early secretory pathway.

   Evidence Immunoprecipitation and genetic epistasis of yeast Yip4 with Tvp and Ypt6/Ric1 components

   PMID:17178117

   Open questions at the time

   • Yeast pathway placement may not transfer to mammalian YIPF6
   • Direct cargo or molecular activity of Yip4 not defined
2. 2012 High

   A forward-genetic loss-of-function model answered what YIPF6 does at the organismal level, revealing an essential role in secretory granule biogenesis in intestinal epithelium.

   Evidence Forward genetic screen, EM, immunocytochemistry and DSS colitis in Yipf6-null mice

   PMID:22802641

   Open questions at the time

   • Molecular mechanism linking YIPF6 to granule formation unresolved
   • No biochemical partners identified in this study
3. 2016 Medium

   Defining membrane topology and localization clarified how YIPF6 is positioned in the Golgi and that it is needed for Golgi structural integrity.

   Evidence Fluorescence microscopy, membrane topology assays and RNAi with Golgi morphology readout in mammalian cells

   PMID:27999994

   Open questions at the time

   • Topology does not reveal catalytic or binding function
   • Mechanism connecting depletion to morphology change unknown
4. 2017 Medium

   Identifying YIPF1/YIPF2 as stable partners showed YIPF6 acts within a Golgi YIP-family complex whose member stability it controls.

   Evidence Reciprocal co-IP, immunofluorescence, BFA washout and siRNA knockdown in mammalian cells

   PMID:28286305

   Open questions at the time

   • Function of the YIPF1/2/6 complex in cargo sorting not defined
   • Single-lab interaction data
5. 2017 Medium

   Overexpression studies in cancer cells linked YIPF6 to extracellular vesicle output and proliferation control, extending its role to post-Golgi secretion.

   Evidence siRNA/overexpression, EV isolation, LC-MS/MS proteomics and APTT assay in 22Rv1 prostate cancer cells

   PMID:28144969

   Open questions at the time

   • Overexpression phenotype may not reflect endogenous function
   • Mechanism connecting YIPF6 to EV biogenesis unresolved
6. 2019 High

   A direct ER cargo-binding role was established, showing YIPF6 gates FGF21 entry into COPII vesicles and thereby controls a metabolic secretory output.

   Evidence Co-IP of ER YIPF6–FGF21 binding, COPII sorting assay, hepatocyte FGF21-KO epistasis and plasma FGF21 in Yipf6-mutant mice on high-fat diet

   PMID:31289229

   Open questions at the time

   • Whether YIPF6 selects other COPII cargoes is unknown
   • Structural basis of FGF21 recognition not defined
7. 2023 Medium

   The TVP23B interaction tied YIPF6 mechanistically to maintenance of Golgi glycosylation enzymes, explaining part of its intestinal homeostasis function.

   Evidence Forward genetic screen, co-IP and Golgi proteomics of TVP23B- and YIPF6-deficient colonocytes with in vivo colitis models

   PMID:37339972

   Open questions at the time

   • How the YIPF6–TVP23B complex retains glycosyltransferases is unclear
   • Direct enzyme cargo not identified

• The unifying molecular activity of YIPF6 — how a single Golgi YIP-family protein coordinates COPII cargo selection, complex-member stabilization, and glycosylation-enzyme retention — remains undefined.
• No structure of YIPF6 or its complexes
• No defined biochemical activity beyond cargo/partner binding
• Relationship between ER FGF21 binding and Golgi complex roles not integrated