A role for cargo in Arf-dependent adaptor recruitment

Area of Science:

• Cell biology
• Molecular biology
• Biochemistry

Background:

• Membrane traffic relies on selective cargo concentration into transport carriers.
• Protein adaptors bind cargo motifs, mediating their sequestration.
• Arf GTPases activate and recruit adaptors to sites of carrier formation, but the initial signal remains unclear.

Purpose of the Study:

• To investigate the specificity and initial recruitment sites of Arf-dependent adaptors (AP-1, GGAs).
• To determine how specific cargo proteins (furin, M6PR, M6PRΔC) influence adaptor recruitment.
• To elucidate the upstream signaling events in cargo-dependent membrane traffic.

Main Methods:

• Examined adaptor recruitment in response to cargo localization in Golgi and endosomes.
• Utilized temperature block, brefeldin A treatment, and recovery experiments.
• Analyzed recruitment of AP-1 and GGAs by M6PR cytoplasmic tail.

Main Results:

• Cargo proteins promote the recruitment of specific Arf-dependent adaptors.
• Adaptor recruitment is compartment-specific and regulated by additional factors.
• M6PR cytoplasmic tail recruits AP-1 and GGAs to recycling endosomes, not Golgi.

Conclusions:

• Cargo proteins act as upstream signals initiating membrane carrier biogenesis.
• Arf activation is spatially and temporally coupled to cargo and adaptor.
• Findings support novel models for cargo-dependent regulation of membrane traffic.