TGN morphology and sorting regulated by prolyl-oligopeptidase-like protein PREPL and AP-1 μ1A
Radhakrishnan, Karthikeyan × Baltes, Jennifer Creemers, John Schu, Peter #
Co. of Biologists
Journal of cell science vol:126 issue:5 pages:1155-63
The AP-1 complex recycles between membranes and the cytoplasm and dissociates from membranes during clathrin-coated-vesicle uncoating, but also independent of vesicular transport. The μ1A N-terminal seventy amino acids are involved in regulating AP-1 recycling. In a yeast-2-hybrid library screen we identified the cytoplasmic prolyl-oligopeptidase-like protein PREPL as an interaction partner of this domain. PREPL overexpression leads to reduced AP-1 membrane binding, whereas reduced PREPL expression increases membrane binding and it impairs AP-1 recycling. Altered AP-1 membrane binding in PREPL-deficient cells mirrors the membrane binding of the mutant AP-1* complex, not able to bind PREPL. Colocalisation of PREPL with residual membrane bound AP-1 can be demonstrated. Patient cell lines deficient in PREPL have an expanded TGN, which could be rescued by PREPL expression. These data demonstrate PREPL as an AP-1 effector, which takes part in the regulation of AP-1 membrane binding. PREPL is highly expressed in brain, and at lower levels also in muscle and kidney, and its deficiency causes hypotonia and growth hormone hyposecretion supporting essential PREPL functions in AP-1-dependent secretory pathways.