The α-helical region in p24γ2 subunit of p24 protein cargo receptor is pivotal for the recognition and transport of glycosylphosphatidylinositol-anchored proteins.

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are group of proteins that depend on p24 cargo receptors for their transport from the endoplasmic reticulum to the Golgi apparatus. The GPI anchor is expected to act as a sorting and transport signal, but so far little is known about the recognition mechanism. In the present study we investigate the GPI-AP transport in cell knockdown of p24γ, the most diverse p24 subfamily. Knockdown of p24γ2 but not of other p24γ family members impaired the transport of a reporter GPI-AP. Restoration of the knockdown-induced phenotype using chimeric constructs between p24γ2 and the related p24γ1 further implied a role of the α-helical region of p24γ2 but not its GOLD domain in the specific binding of GPI-APs. We conclude that motifs in the membrane-adjacent α-helical region of p24γ2 are involved in recognition of GPI-APs and are consequently responsible for the incorporation of these proteins into coat protein complex II-coated transport vesicles.