Fig. 3: C19S represents a context-dependent single-amino-acid transformation emerging in β cells and dendritic cells.
a, Schematic of the PTM/SAV search in crinosome peptidomes isolated from MIN6 cells treated with vehicle or tunicamycin for 2 h. b, Volcano plot showing changes in PTMs and SAVs identified in the crinosome peptidome of MIN6 cells given tunicamycin relative to vehicle treatment. See a complete list in Supplementary Table 2. c, Bar graph showing the abundance of individual insulin peptides with Cys→Ser transformations (each point) identified in the crinosome peptidome of MIN6 cells given vehicle or tunicamycin treatment (n = 16). See a complete list in Supplementary Table 3. d, Stacked bar graph showing the composition of indicated SAVs and PTMs on the B(C19) residue of insulin peptides identified in the crinosome peptidome of MIN6 cells given vehicle or tunicamycin treatment. e, Schematic of the antigen presentation assay to assess the presentation of native or C19S insulin peptides by DCs pulsed with native InsB9-23 and stimulated with different cytokines. f, Bar graph (mean ± s.e.m.) showing C19S transformation from the native InsB9-23 peptide in DCs upon cytokine stimulation, shown as the ratio of S5 to 9B9 T cell responses with or without NAC treatment (n = 3). g, Schematic of MHC-II immunopeptidome analysis of InsB9-23-pulsed DCs stimulated with TNFα with or without NAC. h, Rank plots showing all identified peptides in the DC MHC-II peptidomes ranked by abundance. i, Box plot showing the cumulative abundance of native and C19S insulin peptides identified in the DC MHC-II immunopeptidome analyses (n = 3). In c, n is the number of peptides; each dot is one peptide. In f and i, n is the number of independent experiments; each dot is one biological replicate. Box plot in i shows the minimum and maximum boundaries and the mean (center line). For statistical analysis, two-tailed Wilcoxon signed-rank test was performed for c. RM two-way ANOVA with Sidak’s multiple comparisons tests were performed for f and i. The data represent three independent experiments. Illustrations in a, e and g were partly created with BioRender.com.
