Phase separation of polyubiquitinated proteins in UBQLN2 condensates controls substrate fate.

Autor:	Valentino IM; Department of Chemistry, Villanova University, Villanova, PA 19085., Llivicota-Guaman JG; Department of Chemistry, Villanova University, Villanova, PA 19085., Dao TP; Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244., Mulvey EO; Department of Chemistry, Villanova University, Villanova, PA 19085., Lehman AM; Department of Chemistry, Villanova University, Villanova, PA 19085., Galagedera SKK; Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244., Mallon EL; Department of Chemistry, Villanova University, Villanova, PA 19085., Castañeda CA; Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244., Kraut DA; Department of Chemistry, Villanova University, Villanova, PA 19085.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2024 Aug 13; Vol. 121 (33), pp. e2405964121. Date of Electronic Publication: 2024 Aug 09.
DOI:	10.1073/pnas.2405964121
Abstrakt:	Ubiquitination is one of the most common posttranslational modifications in eukaryotic cells. Depending on the architecture of polyubiquitin chains, substrate proteins can meet different cellular fates, but our understanding of how chain linkage controls protein fate remains limited. UBL-UBA shuttle proteins, such as UBQLN2, bind to ubiquitinated proteins and to the proteasome or other protein quality control machinery elements and play a role in substrate fate determination. Under physiological conditions, UBQLN2 forms biomolecular condensates through phase separation, a physicochemical phenomenon in which multivalent interactions drive the formation of a macromolecule-rich dense phase. Ubiquitin and polyubiquitin chains modulate UBQLN2's phase separation in a linkage-dependent manner, suggesting a possible link to substrate fate determination, but polyubiquitinated substrates have not been examined directly. Using sedimentation assays and microscopy we show that polyubiquitinated substrates induce UBQLN2 phase separation and incorporate into the resulting condensates. This substrate effect is strongest with K63-linked substrates, intermediate with mixed-linkage substrates, and weakest with K48-linked substrates. Proteasomes can be recruited to these condensates, but proteasome activity toward K63-linked and mixed linkage substrates is inhibited in condensates. Substrates are also protected from deubiquitinases by UBQLN2-induced phase separation. Our results suggest that phase separation could regulate the fate of ubiquitinated substrates in a chain-linkage-dependent manner, thus serving as an interpreter of the ubiquitin code. Competing Interests: Competing interests statement:The authors declare no competing interest.
Databáze:	MEDLINE
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