We are delighted that our study, primarily done by Jocelyn and Jun Wei, has just been published in Cellular and Molecular Neuroscience. Here, we demonstrated the cross-modulation between the ubiquitination and phosphorylation of the GluA2 subunit of AMPA receptors by protein kinase C (PKC). Interestingly, this effect is specific for GluA2 as phorbol ester does not potentiate bicuculline-induced ubiquitination of the GluA1 subunit. We envisage that the binding of glutamate on AMPARs in neurons with high level of PKC activity (such as following the activation of mGluRs) will result in subunit-specific regulation of AMPAR ubiquitination and intracellular sorting, which ultimately govern the subunit composition and number of AMPARs, including the Ca2+-permeable AMPARs at synapses.
SFPQ is an abundant and ubiquitous nuclear RNA-binding protein (RBP) that has been implicated in gene regulation and subnuclear body formation. In a study led by Dr. Mihwa Lee (La Trobe University, Melbourne), we report the crystal structure of SFPQ in complex with Zn(II), which reveals an infinite polymer of SFPQ mediated by Zn(II) binding to the protein. The application of Zn(II) to primary cortical neurons induced the cytoplasmic accumulation and aggregation of SFPQ. Mutagenesis of the three Zn(II)-coordinating histidine residues resulted in a significant reduction in the zinc-binding affinity of SFPQ in solution and the Zn(II)-induced cytoplasmic aggregation of SFPQ in cultured neurons. This study, which was published in Nucleic Acids Research, offers a new framework for how metal-induced polymerization of RBPs can induce cytoplasmic aggregation, which are commonly associated with neurodegenerative diseases.
Synaptic Neurobiology Lab