Gavin Ray Owen

Autism spectrum disorder (ASD) has recently been described as a synaptopathy where dysregulation at the level of the synapse is thought to evoke an excitation–inhibition (E/I) imbalance implicated in its pathogenesis. The mechanisms through which alterations in glutamatergic signaling bring about an E/I imbalance remain elusive. Vesicular glutamate transporter 1 (VGLUT1) and postsynaptic density protein‐95 (PSD‐95) are two major regulatory proteins of glutamatergic signaling. This study aimed to determine whether a valproic acid‐induced (VPA) rat model of autism would be associated with changes in the protein expression levels of VGLUT1 and PSD‐95 in the prefrontal cortex (PFC) and cerebellar hemisphere (CH). Sprague‐Dawley rats were obtained from saline control ( n = 3) and VPA‐induced ( n = 3) groups. Consumption of VPA during pregnancy increases the propensity for the development of autism in offspring, making this an effective model for environmentally induced autism. The protein expression levels of VGLUT1 and PSD‐95 were assessed through qualitative western blot analysis from which ratiometric comparisons could be made between control and VPA‐induced rats. In both the PFC and CH, no significant differences were observed in the levels of protein expression of PSD‐95 and VGLUT1 between control and VPA‐induced rats. These findings suggest that the VPA‐induced rat model of autism is not associated with changes in the protein expression levels of PSD‐95 and VGLUT1 in the PFC and CH.

Undergraduate science degrees in South Africa seldom offer explicit courses focussing on improving the disciplinary writing skills required for effectively communicating scientific research. Similarly, most students entering the ‘Honours’ degree in Molecular Medicine at a South African university have not commonly been afforded opportunities to develop appropriate scientific writing and thinking skills. Aspiring to improve writing abilities, in 2017 we introduced a set of writing workshops involving iterative writing activities of scientific report sections with dialogic feedback from the facilitator. This study aimed to interrogate whether the workshops achieved the intended outcomes by conducting a post-course survey to ascertain the perceptions of the Molecular Medicine students. We also compared the grades awarded for the scientific reports in years before and since the implementation of the workshops. Students highlighted numerous ways that the workshops had improved their ability to write sections of a scientific report, while the average grade for the scientific report also increased significantly since the introduction of the workshops. These results reveal that the structure and activities of our workshops can teach scientific writing skills to early-postgraduate level bioscience students with relatively little disruption to the existing curriculum and help inform the format of future writing workshops.

The β‐subunit of the human eukaryotic elongation factor 1 complex (heEF1β) plays a central role in the elongation step in eukaryotic protein biosynthesis, which essentially involves interaction with the α‐ and γ‐subunits (eEF1γ). To biophysically characterize heEF1β, we constructed 3 Escherichia coli expression vector systems for recombinant expression of the full length (FL‐heEF1β), N‐terminus (NT‐heEF1β), and the C‐terminus (CT‐heEF1β) regions of the protein. Our results suggest that heEF1β is predominantly alpha‐helical and possesses an accessible hydrophobic cavity in the CT‐heEF1β. Both FL‐heEF1β and NT‐heEF1β form dimers of size 62 and 30 kDa, respectively, but the CT‐heEF1β is monomeric. FL‐heEF1β interacts with the N‐terminus glutathione transferase‐like domain of heEF1γ (NT‐heEF1γ) to form a 195‐kDa complex or a 230‐kDa complex in the presence of oxidized glutathione. On the other hand, NT‐heEF1β forms a 170‐kDa complex with NT‐heEF1γ and a high molecular weight aggregate of size greater than 670 kDa. Surface plasmon resonance analysis confirmed that (by fitting the Langmuir 1:1 model) FL‐heEF1β associated with monomeric or dimeric NT‐heEF1γ at a rapid rate and slowly dissociated, suggesting strong functional affinity (K_D = 9.6 nM for monomeric or 11.3 nM for dimeric NT‐heEF1γ). We postulate that the N‐terminus region of heEF1β may be responsible for its dimerization and the C‐terminus region of heEF1β modulates the formation of an ordered heEF1β‐γ oligomer, a structure that may be essential in the elongation step of eukaryotic protein biosynthesis.

CD4 is expressed on the surface of specific leukocytes where it plays a key role in the activation of immunostimulatory T-cells and acts as a primary receptor for HIV-1 entry. CD4 has four ecto-domains (D1–D4) of which D1, D2, and D4 contain disulfide bonds. Although disulfide bonds commonly serve structural or catalytic functions, a rare class of disulfide bonds possessing unusually high dihedral strain energy and a relative ease of reduction can impact protein function by shuffling their redox state. D2 of CD4 possesses one such “allosteric” disulfide. While it is becoming accepted that redox exchange of the D2 allosteric disulfide plays an essential role in regulating CD4 activity, the biophysical consequences of its reduction remain incompletely understood. By analyzing the hydrodynamic volume, secondary structure, and thermal stability of the reduced and nonreduced forms of the single D1 and D2 domains, as well as the various redox isomers of two domain CD4, we have shown that ablation of the allosteric disulfide bond in domain 2 results in both a favorable structural collapse and an increase in the stability of CD4. Conversely, ablating the structural disulfide of D1 results in destabilizing structural rearrangements in CD4. These findings expand our understanding of the mechanisms by which oxidoreduction of the D2 allosteric disulfide regulates CD4 function; they reveal the intrinsic disulfide-dependent metastability of D2 and illustrate that redox shuffling of the allosteric disulfide results in previously undescribed conformational changes in CD4 that are likely important for its interaction with its protein partners.