Natural and Designed Proteins Inspired by Extremotolerant Organisms Can Form Condensates and Attenuate Apoptosis in Human Cells

Abstract

Many organisms can survive extreme conditions and successfully recover to normal life. This extremotolerant behavior has been attributed in part to repetitive, amphipathic, and intrinsically disordered proteins that are upregulated in the protected state. Here, we assemble a library of approximately 300 naturally occurring and designed extremotolerance-associated proteins to assess their ability to protect human cells from chemically induced apoptosis. We show that several proteins from tardigrades, nematodes, and the Chinese giant salamander are apoptosis-protective. Notably, we identify a region of the human ApoE protein with similarity to extremotolerance-associated proteins that also protects against apoptosis. This region mirrors the phase separation behavior seen with such proteins, like the tardigrade protein CAHS2. Moreover, we identify a synthetic protein, DHR81, that shares this combination of elevated phase separation propensity and apoptosis protection. Finally, we demonstrate that driving protective proteins into the condensate state increases apoptosis protection, and highlights the ability of DHR81 condensates to sequester caspase-7. Taken together, this work draws a link between extremotolerance-associated proteins, condensate formation, and designing human cellular protection.

In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in Eutardigrada

“…Recently, several reports indicated that recombinant CAHS proteins form fibers or a gel-like lump at high concentrations in vitro, and similar fibrous condensates or aggregates were observed in human cultured cells and Escherichia coli cells ( 23 – 27 ). These gel-like structures are assumed to sustain the structure of a whole cell or to prevent membranes and proteins from cohesion in the cytoplasm.…”

Deciphering the Biological Enigma—Genomic Evolution Underlying Anhydrobiosis in the Phylum Tardigrada and the Chironomid Polypedilum vanderplanki

“…Although these two protein families do not show sequence similarity with canonical LEA proteins, they both form alpha-helical structures under water-deficit conditions or upon TFE treatment, as reported for LEA proteins. Moreover, since 2021, multiple studies have reported the formation of higher-order structures by CAHS proteins [ 92 , 93 , 94 , 95 , 96 ]. These studies argue that purified recombinant CAHS proteins form fiber-like aggregates or gel-like lumps at high concentrations, as is assumed to occur with the onset of desiccation.…”

Tardigrade secretory proteins protect biological structures from desiccation

“…For instance, late embryogenesis-abundant (LEA) proteins are tolerance molecules found in plant seeds and anhydrobiotic species 7 . LEA proteins are mostly unstructured in an aqueous environment and assume helical structure upon desiccation to alleviate damage due to drying 7 , 8 .…”