Inhibiting Hippo pathway kinases releases WWC1 to promote AMPAR-dependent synaptic plasticity and long-term memory in mice

The Serine/Threonine Kinase NDR2 Regulates Integrin Signaling, Synapse Formation, and Synaptic Plasticity in the Hippocampus

Nuclear Dbf2-related (NDR) kinases are core components of the Hippo pathway, which controls neuronal polarity and neurite growth in the central nervous system (CNS). NDR2 is the principal NDR kinase in the mouse CNS, where it has been shown to regulate integrin-dependent dendritic branching as well as growth and plasticity in hippocampal mossy fibers. Given the well-established involvement of integrins in plasticity, we hypothesized that NDR2 might regulate synapse formation and plasticity through integrin-mediated mechanisms. In this study, using constitutive NDR2 null mutant mice, we demonstrate that Ndr2 deficiency leads to a reduction of T788/789 phosphorylated β1 integrin expression at synaptic sites both in the hippocampal area CA1 and in primary hippocampal neurons in vitro. This reduction is associated with decreased synaptic density in both conditions and accompanied by reduced long-term potentiation in the synapses between Schaffer collaterals/commissural fibers and CA1 pyramidal cells, which could be restored by activation of integrins with an arginine-glycine-aspartate-containing peptide, as well as with mild spatial memory deficits. Together, our results suggest that NDR2 is involved in integrin-dependent synapse formation and plasticity in the mouse hippocampus.

PICK1 links KIBRA and AMPA receptor subunit GluA2 in coiled-coil-driven supramolecular complexes

The human memory-associated protein KIBRA regulates synaptic plasticity and trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors, and is implicated in multiple neuropsychiatric and cognitive disorders. How KIBRA forms complexes with and regulates AMPA receptors remains unclear. Here, we show that KIBRA does not interact directly with the AMPA receptor subunit GluA2, but that protein interacting with C kinase 1 (PICK1), a key regulator of AMPA receptor trafficking, can serve as a bridge between KIBRA and GluA2. In contrast, KIBRA can form a complex with GluA1 independent of PICK1. We identified structural determinants of KIBRA-PICK1-AMPAR complexes by investigating interactions and cellular expression patterns of different combinations of KIBRA and PICK1 domain mutants. We find that the PICK1 BAR domain, a coiled-coil structure, is sufficient for interaction with KIBRA, whereas mutation of the PICK1 BAR domain disrupts KIBRA-PICK1-GluA2 complex formation. In addition, KIBRA recruits PICK1 into large supramolecular complexes, a process which requires KIBRA coiled-coil domains. These findings reveal molecular mechanisms by which KIBRA can organize key synaptic signaling complexes.

From postsynaptic neurons to astrocytes: the link between glutamate metabolism, Alzheimer's disease and Parkinson's disease

Glutamate is not only the main excitatory neurotransmitter of the human central nervous system, but also a potent neurotoxin. Therefore, maintaining low-dose, non-toxic extracellular glutamate concentrations between synapses to ensure the reliability of synaptic transmission is essential for maintaining normal physiological functions of neurons. More and more studies have confirmed that the specific pathogenesis of central nervous system diseases (such as Alzheimer's disease) caused by neuronal damage or death due to abnormal inter-synaptic glutamate concentration may be related to the abnormal function of excitatory amino acid transporter proteins and glutamine synthetase on astrocytes, and that the abnormal expression and function of the above two proteins may be related to the transcription, translation, and even modification of both by the process of transcription, translation, and even modification of astrocytes. oxidative stress, and inflammatory responses occurring in astrocytes during their transcription, translation and even modification. Therefore, in this review, we mainly discuss the relationship between glutamate metabolism (from postsynaptic neurons to astrocytes), Alzheimer's disease and Parkinson's disease in recent years.

ATR-hippo drives force signaling to nuclear F-actin and links mechanotransduction to neurological disorders

The mechanical environment is sensed through cell-matrix contacts with the cytoskeleton, but how signals transit the nuclear envelope to affect cell fate decisions remains unknown. Nuclear actin coordinates chromatin motility during differentiation and genome maintenance, yet it remains unclear how nuclear actin responds to mechanical force. The DNA-damage kinase ataxia telangiectasia and Rad3-related protein (ATR) translocates to the nuclear envelope to protect the nucleus during cell motility or compression. Here, we show that ATR drives nuclear actin assembly via recruitment of Filamin-A to the inner nuclear membrane through binding of the hippo pathway scaffold and ATR substrate, RASSF1A. Moreover, we demonstrate how germline RASSF1 mutation disables nuclear mechanotransduction resulting in cerebral cortex thinning and associates with common psychological traits. Thus, defective mechanical-regulated pathways may contribute to complex neurological disorders.

WWC2 modulates GABAA-receptor-mediated synaptic transmission, revealing class-specific mechanisms of synapse regulation by WWC family proteins

The WW and C2 domain-containing protein (WWC2) is implicated in several neurological disorders. Here, we demonstrate that WWC2 interacts with inhibitory, but not excitatory, postsynaptic scaffolds, consistent with prior proteomic identification of WWC2 as a putative component of the inhibitory postsynaptic density. Using mice lacking WWC2 expression in excitatory forebrain neurons, we show that WWC2 suppresses γ-aminobutyric acid type-A receptor (GABAAR) incorporation into the plasma membrane and regulates HAP1 and GRIP1, which form a complex promoting GABAAR recycling to the membrane. Inhibitory synaptic transmission is increased in CA1 pyramidal cells lacking WWC2. Furthermore, unlike the WWC2 homolog KIBRA (kidney/brain protein; WWC1), a key regulator of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) trafficking at excitatory synapses, the deletion of WWC2 does not affect synaptic AMPAR expression. In contrast, loss of KIBRA does not affect GABAAR membrane expression. These data reveal synapse class-selective functions for WWC proteins as regulators of ionotropic neurotransmitter receptors and provide insight into mechanisms regulating GABAAR membrane expression.

Tweaking synaptic plasticity: Deciphering the role of WWC1 in memory opens new therapeutic horizons

WWC1 is a scaffolding protein in the evolutionarily conserved Hippo signaling network and is genetically linked to human memory and synaptic plasticity. In the archives of Science Signaling, Stepan et al. demonstrate the translational potential of modulating WWC1 through pharmacological inhibition of Hippo-pathway kinases to enhance cognition.