FMRP-dependent translational control negatively regulates adapter protein complex 2-mediated endocytosis

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Fragile X syndrome (FXS) is a leading inherited intellectual disability and cause of autism.
• FXS results from the loss of fragile X messenger ribonucleoprotein (FMRP), crucial for mRNA translation and neuronal development.
• FMRP's role in regulating membrane protein localization and expression is not fully understood.

Purpose of the Study:

• To investigate the mechanisms by which FMRP loss affects membrane proteins in neurons.
• To identify specific protein dysregulations in FMRP-deficient neurons.
• To elucidate the role of FMRP in translational control of neuronal protein sorting.

Main Methods:

• Quantitative mass spectrometry to analyze membrane proteins in FMRP-deficient neurons.
• Demonstration of FMRP association with and translational repression of target mRNAs.
• Rescue experiments using shRNA to downregulate AP2B1 levels.

Main Results:

• Identified widespread dysregulation of membrane and associated proteins in FMRP-deficient neurons.
• Found increased levels of clathrin-adapter protein complex 2 (AP-2) subunits (AP2A1, AP2B1) in FXS models.
• Showed that increased AP-2 enhances endocytosis of AMPA receptors, a phenotype rescued by AP2B1 downregulation.

Conclusions:

• FMRP translationally represses AP-2 subunits, controlling protein sorting in neurons.
• Dysregulation of this mechanism contributes to FXS phenotypes, including altered receptor trafficking.
• Reveals a novel translational control pathway impacting neuronal function in FXS.