Abstract
The trans-Golgi network (TGN) is responsible for selectively recruiting newly synthesized cargo into transport carriers for delivery to their appropriate destination. In addition, the TGN is responsible for receiving and recycling cargo from endosomes. The membrane organization of the TGN facilitates the sorting of cargoes into distinct populations of transport vesicles. There have been significant advances in defining the molecular mechanism involved in the recognition of membrane cargoes for recruitment into different populations of transport carriers. This machinery includes cargo adaptors of the adaptor protein (AP) complex family, and monomeric Golgi-localized γ ear-containing Arf-binding protein (GGA) family, small G proteins, coat proteins, as well as accessory factors to promote budding and fission of transport vesicles. Here, we review this literature with a particular focus on the transport pathway(s) mediated by the individual cargo adaptors and the cargo motifs recognized by these adaptors. Defects in these cargo adaptors lead to a wide variety of diseases.
Highlights
In mammalian cells, the trans-Golgi network (TGN) has a distinct morphology, compared to the earlier Golgi cisternae, in that the TGN comprises networks of tubular, branching, and reticulating membranes [1,2]
There is evidence that the cargoes may be segregated into specific TGN membrane micro-domains, and these microdomains are governed by small G proteins and TGN golgins [8,9,10]
Cargo adaptors include the complexes of the adaptor protein (AP) family, as well as the highly-conserved monomeric adaptors, Golgi-localized γ ear-containing ADP ribosylation factor (Arf)-binding proteins (GGAs), which collectively play a central role in the sorting of proteins at the TGN [3,46] (Figure 1B,C)
Summary
The trans-Golgi network (TGN) has a distinct morphology, compared to the earlier Golgi cisternae, in that the TGN comprises networks of tubular, branching, and reticulating membranes [1,2]. Central to the sorting process is the interaction of cytosolic adaptor proteins with specific motifs on the cytoplasmic domains of membrane cargo proteins These adaptor proteins are recruited to the TGN membranes by active membrane-associated Arf small G proteins, which allow them to bind cargoes (Figure 2). The specific recruitment of GDP-bound, but not GTP-bound, Arf and Arf, by calcium-dependent activator protein for secretion 1 (CAPS1) to the TGN has been implicated in the trafficking of dense-core vesicles (DCV) from the Golgi network in rat PC12 cells [31]. Class I and II Arfs at the Golgi, the GTP-bound Arfs may regulate post-Golgi trafficking of specific cargoes via the recruitment of adaptor proteins. A third proposed binding site, which is between the back side of Arf and the central part of AP-1γ subunit trunk domain, leads to the assembly of 2:2 dimer of AP-1 and Arf, and the full activation of AP-1 for cargo binding [37]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
