Arbaciauskaite, M. | Search bioRxiv

bioRxiv2025

Nanobodies targeting hnRNPA2/B1 and tau

Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1) is an RNA-binding protein that mislocalizes to the cytoplasm and forms stress-induced granules in tauopathy and multisystem proteinopathy. It also preferentially interacts with oligomeric tau and is required for tau-mediated neurodegeneration in a mouse model of Alzheimers disease. To study endogenous hnRNPA2/B1 and tau, we generated nanobodies that specifically recognize these proteins. We screened yeast surface display nanobody libraries using an avidity-enhanced screening strategy that enabled selection of binders against short peptide ligands. This led to isolation of anti-hnRNPA2/B1 and anti-tau nanobodies with defined epitopes. Directed evolution of the anti-hnRNPA2/B1 nanobody improved binding affinity by over 20-fold but caused cytoplasmic aggregation, demonstrating a tradeoff between affinity and intracellular behavior. Although the final nanobodies retained modest affinities, they showed robust intracellular colocalization with their targets. Furthermore, fusion to ubiquitin ligase adaptor domains significantly decreased hnRNPA2/B1 and tau levels. Collectively, these nanobodies provide valuable tools for studying hnRNPA2/B1 and tau dynamics in their native cellular context.

bioengineering↗

bioRxiv2022

Yeast biopanning for detecting antibody binding to site-specific phosphorylations in tau

The detection of phosphorylated tau (p-tau) levels in clinical samples is of extreme importance for the detection of Alzheimers Disease (AD) as well as other neurodegenerative diseases. Recent reports show that detecting low levels of p-tau in plasma can be used as a reliable biomarker for detecting AD prior to the onset of memory loss. The ability to detect such low levels of p-tau is dependent on antibodies specific to the post translationally modified protein. However, the need for reliable phospho-site specific antibodies persists due to a lack of approaches for identifying monoclonal antibodies and characterizing non-specific binding. Here, we report a novel approach using the principles of yeast biopanning to create a robust platform that uses synthetic peptides as target antigens. Using peptides as antigens enables screening antibodies against defined post-translational modification sites, particularly for targeting intrinsically disordered proteins such as the human tau protein. To readily assess yeast binding and distinguish non-specific binding, we developed bi-directional expression vectors that allow antibody fragment surface display and intracellular fluorescent protein expression. We show that our platform can specifically and robustly detect a specific site within the p-tau target peptide when compared against non-phosphorylated controls. By improving biopanning parameters, we enabled phospho-specific capture of yeast cells displaying single-chain variable region fragments (scFvs) against p-tau with a wide range of affinities (KD = 0.2 to 60 nM). These results demonstrate that yeast biopanning can robustly capture yeast cells based on phospho-site specific antibody binding, opening doors for facile identification of high-quality monoclonal antibodies.

bioengineering↗