Biology subjects

Jackson, S. M.

Publications and source records attributed to Jackson, S. M..

3 recordsLinked to original sources

bioRxiv2025

Engineered basement membrane mimetic hydrogels to study mammary epithelial morphogenesis and invasion

Reconstituted basement membrane (rBM) products like Matrigel are widely used in 3D culture models of epithelial tissues and cancer. However, their utility is hindered by key limitations, including batch variability, xenogenic contaminants, and a lack of tunability. To address these challenges, we engineered a 3D basement membrane (eBM) matrix by conjugating defined extracellular matrix (ECM) adhesion peptides (IKVAV, YIGSR, RGD) to an alginate hydrogel network with precisely tunable stiffness and viscoelasticity. We optimized the mechanical and biochemical properties of the engineered basement membranes (eBMs) to support mammary acinar morphogenesis in MCF10A cells, similar to rBM. We found that IKVAV-modified, fast-relaxing ({tau}1/2 = 30-150 s), and soft (E = 200 Pa) eBMs best promoted polarized acinar structures. Clusters became invasive and lost polarity only when the IKVAV-modified eBM exhibited both similar stiffness to a malignant breast tumor (E = 4000 Pa) and slow stress relaxation ({tau}1/2 = 600-1100 s). Notably, tumor-like stiffness alone was not sufficient to drive invasion in fast stress relaxing matrices modified with IKVAV. In contrast, RGD-modified matrices promoted a malignant phenotype regardless of mechanical properties. We also utilized this system to interrogate the mechanism driving acinar and tumorigenic phenotypes in response to microenvironmental parameters. A balance in activity between {beta}1- and {beta}4-integrins was observed in the context of IKVAV-modified eBMs, prompting further investigation into the downstream mechanisms. We found differences in hemidesmosome formation and production of endogenous laminin in response to peptide type, stress relaxation, and stiffness. We also saw that inhibiting either focal adhesion kinase or hemidesmosome signaling in IKVAV eBMs prevented acinus formation. This eBM matrix is a powerful, reductionist, xenogenic-free system, offering a robust platform for both fundamental research and translational applications in tissue engineering and disease modeling.

bioengineering↗

bioRxiv2021

Structures of ABCG2 under turnover conditions reveal a key step in drug transport mechanism

ABCG2 is a multidrug transporter expressed widely in the human body. Its physiological substrates include steroid derivatives and uric acid. In addition, it extrudes many structurally diverse cytotoxic drugs from various cells, thus affecting drug pharmacokinetics and contributing to multidrug resistance of cancer cells. Previous studies have revealed structures of ABCG2 bound to transport substrates, nucleotides, small-molecule inhibitors and inhibitory antibodies. However, the transport mechanism is not well-understood because all previous structures described trapped states, where the reaction cycle was halted by the absence of substrates or ATP, mutation of catalytic residues, or the presence of inhibitors. Here we present cryo-EM structures of nanodisc-reconstituted human ABCG2 under turnover conditions containing either the endogenous substrate estrone-3-sulfate or the exogenous substrate topotecan. We found two distinct conformational states in which both the transport substrates and ATP are bound. Whereas the state turnover-1 features more widely separated NBDs and an accessible cavity between the TMDs, turnover-2 features semi-closed NBDs and an almost fully occluded cavity between the TMDs. The transition from turnover-1 to turnover-2 includes conformational changes that link the binding of ATP by the NBDs to the closing of the cytoplasmic side of the TMDs. The size of the substrate appears to control which turnover state corresponds to the main state in the transport cycle. The transition from turnover-1 to turnover-2 is the likely bottleneck or rate-limiting step of the reaction cycle, where the discrimination of substrates and inhibitors occurs. Our results provide a structural basis of substrate specificity of ABCG2 and provide key insight to understand the transport cycle.

biophysics↗

bioRxiv2020

Great Expectations: A Critical Review of and Recommendations for the study of Reward Processing as a Cause and Predictor of Depression

Both human and animal studies support the relationship between depression and reward processing abnormalities, giving rise to the expectation that neural signals of these processes may serve as biomarkers or mechanistic treatment targets. Given the great promise of this research line, we scrutinize those findings and the theoretical claims that underlie them. To achieve this, we apply the framework provided by classical work on causality as well as contemporary approaches to prediction. We identify a number of conceptual, practical, and analytical challenges to this line of research, and use a pre-registered meta-analysis to quantify the longitudinal associations between reward processing aberrations and depression. We also investigate the impact of measurement error on reported data. We find that reward processing abnormalities do not reach levels that would be useful for clinical prediction, yet the evidence thus far does not exclude their possible causal role in depression.

neuroscience↗