PIASx Is a MEF2 SUMO E3 Ligase That Promotes Postsynaptic Dendritic Morphogenesis

Abstract

Postsynaptic morphogenesis of dendrites is essential for the establishment of neural connectivity in the brain, but the mechanisms that govern postsynaptic dendritic differentiation remain poorly understood. Sumoylation of the transcription factor myocyte enhancer factor 2A (MEF2A) promotes the differentiation of postsynaptic granule neuron dendritic claws in the cerebellar cortex. Here, we identify the protein PIASx as a MEF2 SUMO E3 ligase that represses MEF2-dependent transcription in neurons. Gain-of-function and genetic knockdown experiments in rat cerebellar slices and in the postnatal cerebellum in vivo reveal that PIASx drives the differentiation of granule neuron dendritic claws in the cerebellar cortex. MEF2A knockdown suppresses PIASx-induced dendritic claw differentiation, and expression of sumoylated MEF2A reverses PIASx knockdown-induced loss of dendritic claws. These findings define the PIASx-MEF2 sumoylation signaling link as a key mechanism that orchestrates postsynaptic dendritic claw morphogenesis in the cerebellar cortex and suggest novel functions for SUMO E3 ligases in brain development and plasticity.

TIF1γ Protein Regulates Epithelial-Mesenchymal Transition by Operating as a Small Ubiquitin-like Modifier (SUMO) E3 Ligase for the Transcriptional Regulator SnoN1

“…The HA-and GFP-TIF1␥ expression plasmids were generated by cloning full-length human TIF1␥ into pcDNA3 or pEGFP-C1, respectively. The SnoN1/2, SnoN1KdR, and SUMO-SnoN1 expression plasmids have been described previously (20,21,28,29). The mutant TIF1␥ and SnoN expression plasmids were generated by site-directed PCR mutagenesis.…”

“…Analysis of Sumoylation-Analysis of sumoylation was performed as described previously (28,29), with modifications. Briefly, 293T cells cotransfected with expression plasmids for FLAG-TIF1␥, HA-SUMO1, and GFP-SnoN, as indicated, were lysed in 150 l of denaturing buffer (150 mM NaCl, 50 mM Tris-HCl (pH 7.5), 1 mM EDTA, 1% Nonidet P-40, 1% SDS, 1 mM PMSF, 10 mM N-ethylmaleimide, 10 g/ml aprotinin, 10 g/ml pepstatin, 10 g/ml leupeptin, 1 mM dithiothreitol, 50 mM NaF, and 1 mM Na 3 VO 4 ) and sonicated.…”

Cell-intrinsic drivers of dendrite morphogenesis

“…Several transcription factors have been implicated in dendrite morphogenesis in the mammalian brain (Gaudillière et al, 2004;Hand et al, 2005;Shalizi et al, 2006;Ramos et al, 2007;Shalizi et al, 2007;de la Torre-Ubieta et al, 2010). An overarching principle of these studies is that distinct transcription factors may be dedicated to different phases of dendrite development.…”

“…Neuronal activity stimulates calcineurin, which induces the dephosphorylation of MEF2A at Ser408 and promotes a sumoylation-to-acetylation switch at Lys403, thereby activating MEF2A and inhibiting dendritic claw differentiation. The SUMO E3 ligase PIASx (also known as Pias2) induces MEF2 sumoylation and consequently stimulates dendritic claw differentiation in the cerebellar cortex in vivo (Shalizi et al, 2007). Biochemical and nuclear magnetic resonance (NMR) structural studies suggest that Ser408 phosphorylation stimulates the ability of the SUMO E2 enzyme Ubc9 (also known as Ube2i) to trigger SUMO conjugation at Lys403 (Mohideen et al, 2009).…”

SUMOylation of the kainate receptor subunit GluK2 contributes to the activation of the MLK3–JNK3 pathway following kainate stimulation

“…Three SUMO family members are known to exist in the brain of vertebrate: SUMO1, SUMO2, and SUMO3. Accumulating evidence has shown that protein SUMOylation is integral to diverse physiological neuronal functions [3][4][5]. Furthermore, massively increased SUMOylation by both SUMO1 and SUMO2/3 has been observed in both global and focal cerebral ischemic animal models [6][7][8], suggesting a critical role for SUMOylation in neuropathologic processes following ischemic stroke.…”