TMED9
Description
The TMED9 (transmembrane p24 trafficking protein 9) is a protein-coding gene located on chromosome 5.
The p24 protein family is a group of transmembrane proteins that are key components of COPI and COPII-coated vesicles, also known as EMP24/GP25L/p24 family and TMP21-like proteins. This family is named after transmembrane emp24 domain-containing protein 10, discovered in the human brain, which was purported to block the beta-amyloid peptide, a factor implicated in Alzheimer's disease. These proteins are localized to the major organelles of the early secretory pathway: the endoplasmic reticulum and the Golgi apparatus, where they play a role in trafficking between the two compartments. Although all p24 family proteins can be removed in yeast with only a mild phenotype, in mammals some are essential for survival, as demonstrated by the lethality in mice after removal of p24δ1. The p24 family members have been linked to the biogenesis of COPI and COPII-coated vesicles, transporting membrane-bound proteins through the secretory system, and forming the structure of the endoplasmic reticulum and Golgi. Most p24 family proteins exhibit widespread expression in various tissues.
TMED9 appears to play a role in vesicular protein trafficking, particularly in the early secretory pathway. It participates in COPI vesicle-mediated retrograde transport by facilitating the recruitment of coatomer to membranes within this pathway. TMED9 enhances the coatomer-dependent activity of ARFGAP2. It is believed to have a crucial role in retaining p24 complexes specifically within cis-Golgi membranes and contributes to the co-localization of TMED2 and TMED10 in the cis-Golgi network. TMED9 may also be involved in organizing intracellular membranes, including the ER-Golgi intermediate compartment and the Golgi apparatus. It plays a role in the ER localization of PTPN2 isoform PTPB.
TMED9 is also known as GMP25, HSGP25L2G, p24a2, p24alpha2, p25.
