Biology subjects

Wong, A. A.

Publications and source records attributed to Wong, A. A..

3 recordsLinked to original sources

bioRxiv2024

Competitive modulation of Kv1.2 gating by LMAN2 and Slc7a5

Kv1.2 is a prominent ion channel in the CNS, where it regulates neuronal excitability. Kv1.2 structure and function are well understood, but there is less consensus on mechanisms of regulation of Kv1.2 and other potassium channels by auxiliary proteins. We identified novel regulators of Kv1.2 by a mass spectrometry approach. The neutral amino acid transporter Slc7a5 causes a dramatic hyperpolarizing shift of channel activation. In contrast, LMAN2 is a recently identified candidate regulator that has the opposite effect on gating: large depolarizing voltages are required to activate Kv1.2 channels co-expressed with LMAN2. In this study, we characterized the functional interaction between LMAN2 and Slc7a5 on Kv1.2 gating properties and identified key structural elements that underlie sensitivity to each regulator. When LMAN2 and Slc7a5 are expressed together, Kv1.2 activation exhibits a bi-modal voltage-dependence, suggesting two distinct populations of channels regulated either by LMAN2 or Slc7a5, but not both. Using a Kv1.2:1.5 chimeric approach, we identified specific regions between the S1 to S3 segments of the voltage sensing domain (VSD) that are distinct for either Slc7a5 or LMAN2 sensitivity. By replacing either segment with sequence from Kv1.5, modulation by the corresponding regulator was selectively abolished. These results suggest that Slc7a5 and LMAN2 compete for interaction with the Kv1.2 voltage sensor, leading to complex voltage-dependence of channel activity when both regulators are present in the cell.

biophysics↗

bioRxiv2024

Regulation of Kv1.2 redox-sensitive gating by the transmembrane lectin LMAN2

Kv1.2 potassium channels influence excitability and action potential propagation in the nervous system. Unlike closely-related Kv1 channels, Kv1.2 exhibits highly variable voltage-dependence of gating, attributed to regulation by unidentified extrinsic factors. Variable Kv1.2 gating is strongly influenced by the extracellular redox potential, and we demonstrate that Kv1.2 currents in dorsal root ganglion sensory neurons exhibit similar variability and redox sensitivity as observed when the channel is heterologously expressed in cell lines. We used a functional screening approach to test the effects of candidate regulatory proteins on Kv1.2 gating, using patch clamp electrophysiology. Among 52 candidate genes tested, we observed that co-expression with the transmembrane lectin LMAN2 led to a pronounced gating shift of Kv1.2 activation to depolarized voltages in CHO and L(tk-) cell lines, caused by deceleration of activation kinetics. Overexpression of LMAN2 promoted a slow gating mode of Kv1.2 that mimics the functional outcomes of extracellular reducing conditions, and enhanced sensitivity to extracellular reducing agents. In contrast, shRNA-mediated knockdown of endogenous LMAN2 in cell lines reduced Kv1.2 redox sensitivity and gating variability. Kv1.2 sensitivity to LMAN2 is abolished by mutation of neighboring residues F251 and T252 in the intracellular S2-S3 linker, and these also abolish redox-dependent modulation of Kv1.2, suggesting that LMAN2 is an important contributor to the mechanism of redox sensitivity. In conclusion, we identified LMAN2 as a candidate regulatory protein that influences redox-dependent modulation of Kv1.2, and clarified the structural elements of the channel that are required for sensitivity.

biophysics↗

bioRxiv2018

Age-related changes in social behaviours in the 5xFAD mouse model of Alzheimer’s disease

In addition to memory impairments, patients with Alzheimers disease (AD) exhibit a number of behavioural and psychological symptoms that can affect social interactions over the course of the disease. While altered social interactions have been demonstrated in a number of mouse models of AD, many models only recapitulate the initial stages of the disease, and these behavioural changes have yet to be examined over the course of disease progression. By performing a longitudinal study using the 5xFAD mouse model, we have demonstrated that transgenic females exhibit progressive alterations in social investigation compared to wild-type controls. Transgenic females exhibited an age-related reduction in interest for social odours, as well as reduced investigative behaviours towards novel conspecifics in a novel environment. However, transgenic mice exhibited no obvious olfactory deficits, nor any changes in scent-marking behaviour compared to wild-type controls, indicating that changes in investigative behaviour were due to motivation to engage with a social stimulus. This evidence suggests that transgenic 5xFAD females exhibit increased social anxiety in novel environments compared to wildtype controls. Overall, transgenic 5xFAD female mice mimic some features of social withdrawal observed in human AD patients suggesting this strain may be suitable for modelling aspects of the social dysfunction observed in human patients.

neuroscience↗