Immune dysregulation in SHARPIN-deficient mice is dependent on CYLD-mediated cell death.
Proceedings of the National Academy of Sciences of the United States of America
Proc Natl Acad Sci U S A 2021 Dec 14; 118(50):e2001602118
SHARPIN, together with RNF31/HOIP and RBCK1/HOIL1, form the linear ubiquitin chain assembly complex (LUBAC) E3 ligase that catalyzes M1-linked polyubiquitination. Mutations in RNF31/HOIP and RBCK/HOIL1 in humans and Sharpin in mice lead to autoinflammation and immunodeficiency, but the mechanism underlying the immune dysregulation remains unclear. We now show that the phenotype of the Sharpincpdm/cpdm mice is dependent on CYLD, a deubiquitinase previously shown to mediate removal of K63-linked polyubiquitin chains. Dermatitis, disrupted splenic architecture, and loss of Peyer's patches in the Sharpincpdm/cpdm mice were fully reversed in Sharpincpdm/cpdm Cyld-/- mice. We observed enhanced association of RIPK1 with the death-signaling Complex II following TNF stimulation in Sharpincpdm/cpdm cells, a finding dependent on CYLD since we observed reversal in Sharpincpdm/cpdm Cyld-/- cells. Enhanced RIPK1 recruitment to Complex II in Sharpincpdm/cpdm cells correlated with impaired phosphorylation of CYLD at serine 418, a modification reported to inhibit its enzymatic activity. The dermatitis in the Sharpincpdm/cpdm mice was also ameliorated by the conditional deletion of Cyld using LysM-cre or Cx3cr1-cre indicating that CYLD-dependent death of myeloid cells is inflammatory. Our studies reveal that under physiological conditions, TNF- and RIPK1-dependent cell death is suppressed by the linear ubiquitin-dependent inhibition of CYLD. The Sharpincpdm/cpdm phenotype illustrates the pathological consequences when CYLD inhibition fails.
Ang, Rosalind L; Chan, Mark; Legarda, Diana; Sundberg, John P; Sun, Shao-Cong; Gillespie, Virginia L; Chun, Nicholas; Heeger, Peter S; Xiong, Huabao; Lira, Sergio A; and Ting, Adrian T, "Immune dysregulation in SHARPIN-deficient mice is dependent on CYLD-mediated cell death." (2021). Faculty Research 2021. 260.