Biology subjects

Scheutzow, A.

Publications and source records attributed to Scheutzow, A..

3 recordsLinked to original sources

bioRxiv2025

HSP-1-Specific Nanobodies Alter Chaperone Function in vitro and in vivo

Targeted regulation of 70 kilodalton Heat Shock Protein (HSP70) chaperones, particularly the essential cognate heat shock protein (HSC70) and its Caenorhabditis elegans ortholog, HSP-1, may hold the key to improving cellular proteostasis and ameliorating aging-associated conditions linked to protein misfolding and aggregation. However, tools to selectively modulate HSP70 chaperone activity remain elusive. In this study, we pioneer the development of two novel nanobodies, B12 and H5, which specifically bind to both recombinant and endogenous HSP-1. We show that these nanobodies, differing by only two amino acids in their complementarity-determining regions, bind specifically to HSP-1 and effectively reduce both HSP-1 ATPase activity and protein folding capacity in a dose-dependent manner in vitro. We further demonstrate in vivo expression of B12, but not H5, in transgenic C. elegans strains reduces heat-stress survival and proteotoxic-stress resistance, mirroring the effects of hsp-1 knockdown via RNA interference. Our findings suggest that these nanobodies can serve as effective and specific tools for modulating HSP-1 chaperone activity in vivo. These discoveries provide a foundation for future research exploring the therapeutic potential of HSP70-targeting nanobodies in aging and protein misfolding diseases.

biochemistry↗

bioRxiv2024

E3 ligase recruitment by UBQLN2 protects substrates from proteasomal degradation

Ubiquilins are a family of proteins critical to cellular proteostasis that are also linked to several neurodegenerative diseases, with specific mutations in UBQLN2 causing dominant, X-linked ALS. Despite an initial characterization as proteasomal shuttle factors, Ubiquilins have paradoxically been reported to stabilize numerous substrates. The basis of this triage decision remains enigmatic. Many other fundamental aspects of Ubiquilin function are unclear at the mechanistic level, such as the physiological significance of Ubiquilin phase separation, the unique role of each Ubiquilin paralog, and the mechanistic defects of ALS mutants. To address these questions, we utilized a library of triple knockout (TKO) rescue cell lines with physiological expression of single Ubiquilin paralogs or disease mutants in an isogenic background. Our findings reveal that UBQLN2 has a unique ability to protect substrates from degradation and that substrate stabilization correlates with the recruitment of multiple E3 ligases, including SCFbxo7. We propose that E3 ligase recruitment promotes UBQLN2 phase separation, which protects substrates from proteasomal degradation. Consistent with this model, we demonstrate that ALS mutants, which were previously shown to have altered phase separation properties, also show a defect in substrate stabilization. Finally, we show that substrate stabilization appears to be a general feature of proteins that interact with the UBQLN2 Sti1 domains as amyloid precursor protein (APP) is also protected from proteasomal degradation by the formation of biomolecular condensates. This proposal unifies many existing observations in the field and presents a new paradigm for understanding Ubiquilin function in neurodegenerative disease.

biochemistry↗

bioRxiv2019

Complexin suppresses spontaneous exocytosis by capturing the membrane-proximal regions of VAMP2 and SNAP25

The neuronal protein complexin contains multiple domains that exert both clamping and facilitatory functions to tune spontaneous and action potential triggered synaptic release. We address the clamping mechanism and show that the accessory helix of complexin arrests the assembly of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex that forms the core machinery of intracellular membrane fusion. In a reconstituted fusion assay, site- and stage-specific photo-cross-linking reveals that prior to fusion the complexin accessory helix laterally binds the membrane-proximal C-terminal ends of SNAP25 and VAMP2. Corresponding complexin interface mutants selectively increase spontaneous release of neurotransmitter in living neurons, implying that the accessory helix suppresses final zippering/assembly of the SNARE four-helix bundle by restraining VAMP2 and SNAP25.

neuroscience↗