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The 46-kDa mannose 6-phosphate receptor contains multiple binding sites for clathrin adaptors
S Höning1, M Sosa, A Hille-Rehfeld
1Institute for Biochemistry II, University of Göttingen, 37073 Göttingen, Germany.
Abstract:
The two known mannose 6-phosphate receptors (MPR46 and MPR300) both mediate the transport of Man-6-P-containing lysosomal proteins to lysosomes. However, the MPRs cannot be detected in lysosomes, instead they recycle between the plasma membrane and endosomes and between endosomes and the trans-Golgi network. Both, endocytosis from the plasma membrane and budding of transport vesicles from the trans-Golgi network involves the interaction of the receptor with the clathrin-coated vesicles-associated protein complexes AP1 and AP2. We have analyzed this interaction between the Golgi-restricted AP1 complex and the plasma membrane-restricted AP2 complex with the MPR46 tail in vitro by using a biosensor. AP1 and AP2 both bind to and dissociate from the MPR46 tail with similar kinetics. Using synthetic peptides corresponding to different MPR receptor tail regions in inhibition and binding studies, a common high affinity binding site for AP1 and AP2 and two separate high affinity binding sites for AP1 and AP2, respectively, were identified.
Insights
Mannose 6-phosphate receptors (MPRs) deliver lysosomal proteins. Researchers studied MPR46 interactions with AP1 and AP2 protein complexes, finding common and distinct binding sites crucial for receptor trafficking.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mannose 6-phosphate receptors (MPRs), specifically MPR46 and MPR300, are essential for targeting lysosomal proteins to lysosomes.
- MPRs undergo continuous recycling between the plasma membrane, endosomes, and the trans-Golgi network, rather than accumulating in lysosomes.
- This recycling process involves interactions with adaptor protein complexes AP1 and AP2, which are critical for clathrin-coated vesicle formation.
Purpose of the Study:
- To investigate the in vitro interaction between the MPR46 receptor tail and the AP1 and AP2 adaptor protein complexes.
- To characterize the binding kinetics and identify specific binding sites for AP1 and AP2 on the MPR46 tail.
Main Methods:
- Utilized a biosensor assay to analyze the binding and dissociation kinetics of AP1 and AP2 with the MPR46 tail.
- Employed synthetic peptides representing different regions of the MPR46 tail in binding and inhibition studies.
Main Results:
- Both AP1 and AP2 complexes exhibited similar binding and dissociation kinetics with the MPR46 tail.
- Analysis revealed a common high-affinity binding site for both AP1 and AP2 on the MPR46 tail.
- Additionally, two distinct high-affinity binding sites were identified, one specific to AP1 and the other to AP2.
Conclusions:
- The MPR46 tail possesses distinct and overlapping binding sites for AP1 and AP2.
- These interactions are crucial for the differential sorting and trafficking of MPR46 between the plasma membrane, endosomes, and the trans-Golgi network.
- Understanding these binding dynamics provides insight into the molecular mechanisms governing lysosomal protein transport.