Biology subjects

Sugden, A.

Publications and source records attributed to Sugden, A..

3 recordsLinked to original sources

bioRxiv2025

A Proteolytic Switch: USP5 controls SDE2 function via UBL-directed cleavage

Proteolytic processing is a critical regulatory mechanism in eukaryotic cells, yet the molecular identities and mechanisms underlying these events often remain elusive. Silencing Defective 2 (SDE2) is an essential human protein involved in multiple aspects of genome regulation, including DNA repair, ribosome biogenesis, and mRNA splicing. SDE2 is expressed with an N-terminal ubiquitin-like domain (SDE2UBL) which must be proteolytically cleaved to release the functional C-terminal domain (SDE2CT). This cleavage not only activates SDE2CT but also marks it for subsequent degradation, highlighting the importance of this tightly regulated processing. Despite the crucial role of this cleavage event, the human protease responsible has remained unknown. Here, we identify that the deubiquitinating enzyme, ubiquitin-specific protease 5 (USP5), catalyses the cleavage of SDE2. Using an integrated workflow combining biochemical assays, proteomic profiling, and mass spectrometry, we demonstrate that USP5 selectively processes SDE2 in vitro and in cell. To validate the specificity of this interaction, we engineered SDE2UBL into an activity-based probe, and developed a cellular reporter assay, both of which confirmed USP5 as the primary effector. Biophysical analysis further revealed that SDE2UBL binds to USP5 with similar characteristics to ubiquitin, albeit with reduced affinity, supporting a mechanism of substrate mimicry. Together, these findings uncover a novel regulatory axis for SDE2 function, highlighting an underappreciated role for DUBs in regulating protein maturation events. They also establish a versatile approach for identifying and validating substrate-protease interactions with broader implications for the study of post-translational regulation.

biochemistry↗

bioRxiv2024

Cortical Reactivations Modulated by Local InhibitoryCircuits Mediate Memory Consolidation

Highly salient events activate neurons across various brain regions. During subsequent rest or sleep, the activity patterns of these neurons often correlate with those observed during the preceding experience. Growing evidence suggests that these reactivations play a crucial role in memory consolidation, the process by which experiences are solidified in cortical networks for long-term storage. Here, we demonstrate that reactivations in the lateral visual cortex are vital for the consolidation of visual association learning. By employing longitudinal two-photon Ca2+ imaging alongside paired LFP recordings in the hippocampus and cortex, we show that targeted manipulation of PV+ inhibitory neurons in the lateral visual cortex after daily training selectively attenuated cue-specific reactivations and learning, with no apparent effect on normal network function during training. In contrast, reactivations in the control group were biased towards salient cues, aligned with learning process and persisted for hours after training had ended. Overall, our results underscore a crucial role for cortical reactivations in memory consolidation.

neuroscience↗

bioRxiv2019

State-specific gating of salient cues by midbrain dopaminergic input to basal amygdala

Basal amygdala (BA) neurons guide associative learning via acquisition of responses to stimuli that predict salient appetitive or aversive outcomes. We examined the learning- and state-dependent dynamics of BA neurons and ventral tegmental area dopamine axons that innervate BA (VTADA[->]BA) using two-photon imaging and photometry in behaving mice. BA neurons did not respond to arbitrary visual stimuli, but acquired responses to stimuli that predicted either rewards or punishments. Most VTADA[->]BA axons were activated by both rewards and punishments, and acquired responses to cues predicting these outcomes during learning. Responses to cues predicting food rewards in VTADA[->]BA axons and BA neurons in hungry mice were strongly attenuated following satiation, while responses to cues predicting unavoidable punishments persisted or increased. Therefore, VTADA[->]BA axons may provide a reinforcement signal of motivational salience that invigorates adaptive behaviors by promoting learned responses to appetitive or aversive cues in distinct, intermingled sets of BA excitatory neurons.

neuroscience↗