Neurons maintain constant levels of excitability using homeostatic scaling, which adjusts relative synaptic strength in response to large changes in overall activity. While previous studies have catalogued the transcriptomic and proteomic changes associated with scaling, the resulting alterations in synaptic protein interaction networks (PINs) are less well understood. Here, we monitor a glutamatergic synapse PIN composed of 380 binary interactions among 21 protein members to identify protein complexes altered by synaptic scaling. In cultured cortical neurons, we observe widespread bidirectional PIN alterations with up-versus downscaling. In the barrel cortex, the PIN response to 48 hours of sensory deprivation exhibits characteristics of both upscaling and downscaling, consistent with emerging models of excitatory/inhibitory balance in cortical plasticity. Mice lacking Homer1 or Shank3B do not undergo normal PIN rearrangements, suggesting that these Autism Spectrum Disorder (ASD)-linked proteins serve as structural hubs for synaptic homeostasis. Our approach demonstrates how previously identified RNA and protein-level changes induced during homeostatic scaling translate into functional PIN alterations.
Statement: Loss of JNK signaling reduces growth cone branching frequency, limits 17 interstitial side branch duration, alters rate and amplitude of nucleokinesis, and mislocalizes 18 centrosomes and primary cilia in migrating cortical interneurons. ABSTRACT 34Aberrant migration of inhibitory interneurons can alter the formation of cortical circuitry and lead 35 to severe neurological disorders including epilepsy, autism, and schizophrenia. However, 36 mechanisms involved in directing the migration of these cells remain incompletely understood. 37In the current study, we used live-cell confocal microscopy to explore the mechanisms by which 38 the c-Jun NH 2 -terminal kinase (JNK) pathway coordinates leading process branching and 39 nucleokinesis, two cell biological processes that are essential for the guided migration of cortical 40 interneurons. Pharmacological inhibition of JNK signaling disrupts the kinetics of leading 41 process branching, rate and amplitude of nucleokinesis, and leads to the rearward 42 mislocalization of the centrosome and primary cilium to the trailing process. Genetic loss of Jnk 43 from interneurons corroborates our pharmacological observations and suggests that important 44 mechanics of interneuron migration depend on the intrinsic activity of JNK. These findings 45 suggest that JNK signaling regulates leading process branching, nucleokinesis, and the 46 trafficking of centrosomes and cilia during interneuron migration, and further implicates JNK 47 signaling as an important mediator of cortical development. 48 49 SYMBOLS AND ABBREVIATIONS 50 MGE: Medial ganglionic eminence 51 CGE: Caudal ganglionic eminence 52 JNK: c-Jun NH 2 -terminal kinase 53 Dcx: Doublecortin 54 Cetn2-mCherry: Centrin2-mCherry 55 Dlx5/6-CIE: Dlx5/6-Cre-IRES-EGFP
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