Biology subjects

Miller, A. P.

Publications and source records attributed to Miller, A. P..

5 recordsLinked to original sources

bioRxiv2026

CaMKII T286 autophosphorylation is not propagated at basal Ca2+ levels and is required only for the induction phase of LTP

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) and its autophosphorylation at T286 (P-T286) mediates long-term potentiation (LTP) of synaptic strength. CaMKII forms stable 12-meric holoenzymes, but exchange of its subunits is proposed to propagate the P-T286 state beyond dephosphorylation or degradation of individual subunits. However, a recent study questioned subunit exchange and instead proposed P-T286 propagation by trans-holoenzyme phosphorylation. We show here that both subunit exchange and trans-holoenzyme P-T286 can occur (although cis-holoenzyme P-T286 is much preferred), but that neither mechanism propagates P-T286 at basal cellular Ca2+ levels (50-100 nM) in absence of further Ca2+-stimuli. Functionally, we show that after theta-burst stimulation (TBS), P-T286 is required only during the first minutes of LTP induction that prime for subsequent LTP expression, but neither for LTP expression itself nor for LTP maintenance. These results indicate that P-T286 of CaMKII does not self-perpetuate and does not mediate storage but computation of synaptic information.

neuroscience↗

bioRxiv2025

Assessing Knowledge, Uptake and Factors associated with cervical cancer screening among women in selected communities of Wakiso District in Uganda: A population-based study

BackgroundUganda has the highest prevalence and incidence of cervical cancer in the East African region, with 80% of women diagnosed at advanced stage when survival is minimal. Literature on uptake of cervical cancer screening is limited in Uganda and thus womens knowledge and uptake of cervical cancer screening in the general population remains unknown. This study examined this gap of knowledge among women aged 25-65 years, across rural, urban and semi urban communities in a Ugandan district to inform design of targeted future cervical cancer screening programs in the country. MethodsThis descriptive cross-sectional study was conducted in Wakiso district, Uganda in May 2024 among 783 eligible women. Face-to-face interviews were conducted. Uptake of cervical cancer screening (outcome of interest)) was dichotomously (yes/no) assessed. Knowledge of cervical cancer disease was assessed using the AWACAN validated tool, knowledge of cervical cancer screening was assessed using a set of ten (10) questions adapted from previous studies elsewhere, and all were measured on a Likert scale. Univariate, bivariate, and multivariable Poisson regression models with robust variance were performed using Stata software version 17. ResultsRespondents median age was 31 years (IQR 27-39 years). Majority (89.5%, 701/783) had heard of cervical cancer, and 90.6% (635/701) were aware of screening. Median knowledge score on signs and symptoms, risk factors and cervical cancer screening was 8.0 (IQR= 5-10), 8.0 (IQR= 5-11) and 7.0 (IQR= 4-10) respectively, and 54.3% had high knowledge about cervical cancer screening. Uptake of cervical cancer screening was 33.4%. Living in urban areas (aPR = 1.41, 95% CI: 1.05 - 1.88), being the ages 40-49 years (aPR = 1.76, 95% CI: 1.36 - 2.27), 50 years and above (APR = 2.16, 95% CI: 1.53 - 3.04), smoking (aPR = 1.39, 95% CI: 1.05 - 1.86), partner involvement (aPR = 2.61, 95% CI: 2.12-3.21), high knowledge about cervical cancer screening (aPR = 3.29, 95% CI: 2.35-4.60), and living with HIV (aPR = 1.66, 95% CI: 1.66-2.13) were significantly associated with higher uptake of cervical cancer screening among women in this setting. ConclusionKnowledge of cervical cancer screening was high, but the uptake of cervical cancer screening was lower than the recommended population coverage by WHO and Uganda national guidelines. There is need to improve accessibility to cervical cancer screening, increase nationwide cervical cancer awareness campaigns focusing on high-risk age groups and design targeted, tailored, culturally and socially sensitive interventions for young women aged 25-39 years to improve cervical cancer screening in Uganda.

scientific communication and education↗

bioRxiv2024

Mechanism of small heat shock protein client sequestration and induced polydispersity

Small heat shock proteins (sHSPs) act as first responders during cellular stress by recognizing and sequestering destabilized proteins (clients), preventing their aggregation and facilitating downstream refolding or degradation1-3. This chaperone function is critically important to proteostasis, conserved across all kingdoms of life, and associated with various protein misfolding diseases in humans4,5. Mechanistic insights into how sHSPs sequester destabilized clients have been limited due to the extreme molecular plasticity and client-induced polydispersity of sHSP/client complexes6-8. Here, we present high-resolution cryo-EM structures of the sHSP from Methanocaldococcus jannaschii (mjHSP16.5) in both the apo-state and in an ensemble of client-bound states. The ensemble not only reveals key molecular mechanisms by which sHSPs respond to and sequester client proteins, but also provides insights into the cooperative nature of chaperone-client interactions. Engagement with destabilized client induces a polarization of stability across the mjHSP16.5 scaffold, proposed to facilitate higher-order assembly and enhance client sequestration capacity. Some higher-order sHSP oligomers appear to form through simple insertion of dimeric subunits into new geometrical features, while other higher-order states suggest multiple sHSP/client assembly pathways. Together, these results provide long-sought insights into the chaperone function of sHSPs and highlight the relationship between polydispersity and client sequestration under stress conditions.

biophysics↗

bioRxiv2023

The α-crystallin chaperones undergo a quasi-ordered co-aggregation process in response to saturating client interaction

Small heat shock proteins (sHSPs) are ATP-independent chaperones vital to cellular proteostasis, preventing protein aggregation events linked to various human diseases including cataract. The -crystallins, A-crystallin (Ac) and B-crystallin (Bc), represent archetypal sHSPs that exhibit complex polydispersed oligomeric assemblies and rapid subunit exchange dynamics. Yet, our understanding of how this plasticity contributes to chaperone function remains poorly understood. This study investigates structural changes in Ac and Bc during client sequestration under varying degree of chaperone saturation. Using biochemical and biophysical analyses combined with single-particle electron microscopy (EM), we examined Ac and Bc in their apo-states and at various stages of client-induced co-aggregation, using lysozyme as a model client. Quantitative single-particle analysis unveiled a continuous spectrum of oligomeric states formed during the co-aggregation process, marked by significant client-triggered expansion and quasi-ordered elongation of the sHSP scaffold. These structural modifications culminated in an apparent amorphous collapse of chaperone-client complexes, resulting in the creation of co-aggregates capable of scattering visible light. Intriguingly, these co-aggregates maintain internal morphological features of highly elongated sHSP scaffolding with striking resemblance to polymeric -crystallin species isolated from aged lens tissue. This mechanism appears consistent across both Ac and Bc, albeit with varying degrees of susceptibility to client-induced co-aggregation. Importantly, our findings suggest that client-induced co-aggregation follows a distinctive mechanistic and quasi-ordered trajectory, distinct from a purely amorphous process. These insights reshape our understanding of the physiological and pathophysiological co-aggregation processes of sHSPs, carrying potential implications for a pathway toward cataract formation.

biophysics↗

bioRxiv2021

Conserved and divergent features of neuronal CaMKII holoenzyme structure, function, and high-order assembly

Neuronal CaMKII holoenzymes (- and {beta}-isoforms) enable molecular signal computation underlying learning and memory, but also mediate excitotoxic neuronal death. Here, we provide a comparative analysis of these signaling devices, using single particle EM in combination with biochemical and live-cell imaging studies. In the basal state, both isoforms assembled mainly as 12-mers (but also 14-mers, and even 16-mers for the {beta}-isoform). CaMKII and {beta}-isoforms adopted an ensemble of extended activatable states (with average radius of 12.6 versus 16.8 nm, respectively), characterized by multiple transient intra- and inter-holoenzyme interactions associated with distinct functional properties. The extended state of CaMKII{beta} allowed EM analysis to directly resolve intra-holoenzyme kinase-domain dimers that could enable the cooperative activation mechanism by calmodulin, which was found for both isoforms. Surprisingly, high-order CaMKII clustering mediated by inter-holoenzyme kinase-domain dimerization was reduced for the {beta} isoform for both basal and excitotoxicity-induced clusters, both in vitro and in neurons.

molecular biology↗