Koentgen, F. | Search bioRxiv

bioRxiv2022

Ubiquitination of the GluA1 subunit of AMPA receptors is required for synaptic plasticity, memory and cognitive flexibility

Activity-dependent changes in the number of AMPA-type glutamate receptors (AMPARs) at the synapse underpin the expression of long-term potentiation (LTP) and long-term depression (LTD), cellular correlates of learning and memory. Post-translational ubiquitination has emerged as a key regulator of the trafficking and surface expression of AMPARs, with ubiquitination of the GluA1 subunit at Lys-868 controlling the post-endocytic sorting of the receptors into the late endosome for degradation, and thereby regulating their stability at synapses. However, the physiological significance of GluA1 ubiquitination remains unknown. In this study, we generated mice with a knock-in mutation in the major GluA1 ubiquitination site (K868R) to investigate the role of GluA1 ubiquitination in synaptic plasticity, learning and memory. Our results reveal that these mice have normal basal synaptic transmission but exhibit enhanced LTP and deficits in LTD. They also display deficits in short-term spatial memory and cognitive flexibility. These findings underscore the critical roles of GluA1 ubiquitination for bidirectional synaptic plasticity and cognition.

neuroscience↗

bioRxiv2021

EHF is essential for epidermal and colonic epithelial homeostasis and suppresses Apc-initiated colonic tumorigenesis

BackgroundEts homologous factor (EHF) is a member of the epithelial-specific Ets (ESE) transcription factors. EHF is specifically expressed in epithelial tissues, however its role in development and epithelial homeostasis is largely uncharacterized. MethodsWe generated a novel mouse strain in which the Ets DNA binding domain (exon 8) of Ehf was flanked by loxP sites (EhfLox/Lox). To inactivate Ehf in the whole body, EhfLox/Lox mice were crossed to CMVCre mice, which were then bred out to generate germline Ehf null (Ehf-/-) mice. To inactivate Ehf specifically in the intestinal epithelium, EhfLox/Lox mice were bred to tamoxifen-inducible VillinCre-ERT2 mice. EhfLox/Lox mice were also crossed to tamoxifen-inducible Cdx2CreERT2; ApcLox/+ mice to determine the impact of Ehf deletion on Apc-initiated colon cancer development. ResultsTranscripts encoding the Ets binding domain of EHF were effectively deleted in all tissues in Ehf-/- mice. Ehf-/- mice were born at the expected Mendelian ratio, but showed reduced body weight gain and developed a series of pathologies during their lifespan that led the majority of Ehf-/- mice to reach an ethical endpoint within one year of age. Most prominent of these were the development of papillomas in the chin, and abscesses in the preputial glands (males) or vulvae (females) which showed evidence of Staphylococcus and Proteus infection. Consistent with the development of papillomas, the epidermis of Ehf-/- mice showed evidence of mild hyperplasia. A subset of Ehf-/- mice also developed cataracts and corneal ulcers. EHF is highly expressed in the colonic epithelium and Ehf-/- mice displayed increased susceptibility to dextran sodium sulphate-induced colitis. This phenotype was confirmed in intestinal-specific Ehf knockout mice, and histopathological analyses revealed reduced numbers of goblet cells and extensive transcriptional reprogramming in the colonic epithelium. Finally, colon-specific deletion of Ehf enhanced Apc-initiated adenoma development, unveiling a novel, tumour suppressive role for EHF in colorectal cancer. ConclusionThe Ets DNA-binding domain of EHF is essential for post-natal homeostasis of the epidermis and colonic epithelium, and functions as a tumour suppressor in the colon.

cell biology↗