Biology subjects

Heissler, S.

Publications and source records attributed to Heissler, S..

3 recordsLinked to original sources

bioRxiv2022

Competition between myosin II and βH-Spectrin regulates cytoskeletal tension

Spectrins are membrane cytoskeletal proteins generally thought to function as heterotetramers comprising two -spectrins and two {beta}-spectrins. They influence cell shape and Hippo signaling, but the mechanism by which they influence Hippo signaling has remained unclear. We have investigated the role and regulation of the Drosophila {beta}-heavy Spectrin ({beta}H-Spectrin, encoded by the karst gene) in wing imaginal discs. Our results establish that {beta}H-Spectrin regulates Hippo signaling through the Jub biomechanical pathway due to its influence on cytoskeletal tension. While we find that -Spectrin also regulates Hippo signaling through Jub, unexpectedly, we find that {beta}H-Spectrin localizes and functions independently of -Spectrin. Instead, {beta}H-Spectrin co-localizes with and reciprocally regulates and is regulated by myosin. In vivo and in vitro experiments support a model in which {beta}H-Spectrin and myosin directly compete for binding to apical F-actin. This competition can explain the influence of {beta}H-Spectrin on cytoskeletal tension and myosin accumulation. It also provides new insight into how {beta}H-Spectrin participates in ratcheting mechanisms associated with cell shape change.

cell biology↗

bioRxiv2022

Structural Mechanisms of Actin Isoforms

Actin isoforms organize into distinct networks that are essential for the normal function of eukaryotic cells. Despite a high level of sequence and structure conservation, subtle changes in their design principles determine the interaction with myosin motors and actin-binding proteins. The functional diversity is further increased by posttranslational modifications (PTMs). Therefore, identifying how the structure of actin isoforms relates to function is important for our understanding of normal cytoskeletal physiology. Here, we report the high-resolution structures of filamentous skeletal -actin (3.37[A]), cardiac -actin (3.07[A]), {beta}-actin (2.99[A]), and {gamma}-actin (3.38[A]) in the Mg2+{middle dot}ADP state with their native PTMs. The structures revealed isoform-specific conformations of the N-terminus that shifts closer to the filament surface upon myosin binding, thereby establishing isoform-specific interfaces. Retropropagated structural changes further show that myosin binding modulates actin filament structure. Further, our structures enabled us to reveal the location of disease-causing mutations and to analyze them with respect to known locations of PTMs. Collectively, the previously unknown structures of single-isotype, posttranslationally modified bare cardiac -actin, {beta}-actin, and {gamma}-actin reveal general principles, similarities, and differences between isoforms. They complement the repertoire of known actin structures and allow for a comprehensive understanding of in vitro and in vivo functions of actin isoforms.

biochemistry↗

bioRxiv2022

Compound interaction screen on a photoactivatable cellulose membrane (CISCM) identifies drug targets

Identifying the protein targets of drugs is an important but tedious process. Existing proteomic approaches enable unbiased target identification but lack the throughput needed to screen larger compound libraries. Here, we present a compound interaction screen on a photoactivatable cellulose membrane (CISCM) that enables target identification of several drugs in parallel. To this end, we use diazirine-based undirected photoaffinity labeling (PAL) to immobilize compounds on cellulose membranes. Functionalized membranes are then incubated with protein extract and specific targets are identified via quantitative affinity purification and mass spectrometry. CISCM reliably identifies known targets of natural products in less than three hours of analysis time per compound. In summary, we show that combining undirected photoimmobilization of compounds on cellulose with quantitative interaction proteomics provides an efficient means to identify the targets of natural products.

biochemistry↗