Assembly-dependent Structure Formation Shapes Human Interleukin-23 versus Interleukin-12 Secretion

• Published in: Journal of molecular biology Vol. 435; no. 23; p. 168300
• Main Authors: Aschenbrenner, Isabel, Siebenmorgen, Till, Lopez, Abraham, Parr, Marina, Ruckgaber, Philipp, Kerle, Anna, Rührnößl, Florian, Catici, Dragana, Haslbeck, Martin, Frishman, Dmitrij, Sattler, Michael, Zacharias, Martin, Feige, Matthias J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2023
• Subjects: chaperones; interleukins; protein assembly; protein folding; protein secretion; protein folding; chaperones; protein assembly; protein secretion; interleukins
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2023.168300

[Display omitted] •Subunit competition influences the secretion of heterodimeric cytokines.•Rational engineering enabled the design of a folding-competent human IL-23α.•Stabilized IL-23α is less dependent on molecular chaperones.•This engineered variant skews the balance of IL-23 versus IL-12 secretion.•Nature possibly evolved assembly-dependent subunits to regulate IL secretion ratios. Interleukin 12 (IL-12) family cytokines connect the innate and adaptive branches of the immune system and regulate immune responses. A unique characteristic of this family is that each member is anα:βheterodimer. For human αsubunits it has been shown that they depend on theirβsubunit for structure formation and secretion from cells. Since subunits are shared within the family and IL-12 as well as IL-23 use the same βsubunit, subunit competition may influence cytokine secretion and thus downstream immunological functions. Here, we rationally design a folding-competent human IL–23α subunit that does not depend on itsβsubunit for structure formation. This engineered variant still forms a functional heterodimeric cytokine but shows less chaperone dependency and stronger affinity in assembly with its βsubunit. It forms IL-23 more efficiently than its natural counterpart, skewing the balance of IL-12 and IL-23 towards more IL-23 formation. Together, our study shows that folding-competent human IL-12 familyαsubunits are obtainable by only few mutations and compatible with assembly and function of the cytokine. These findings might suggest that human α subunits have evolved for assembly-dependent folding to maintain and regulate correct IL–12 family member ratios in the light of subunit competition.