Engineering the insulin signal peptide to protect human pancreatic beta cells from autoimmune destruction.

Autoreactive T cells that destroy beta cells in type 1 diabetes are largely targeting insulin signal peptide fragments. HLA knockout beta-cells have been proposed to create hypo-immune cells, but this strategy poses significant tumorigenic risks. Alternatively, we hypothesized that insulin signal peptide modification would give rise to beta cells evading autoimmune recognition while maintaining insulin functionality. We developed human beta-cell lines lacking endogenous insulin and complemented them with insulin-carrying signal peptides from different hormones including chromogranin-A. We evaluated insulin synthesis, processing, secretion, activity, and immune evasion. Chromogranin-A signal peptide substitution directed insulin expression, maturation, and secretion, maintaining physiological proinsulin/insulin ratios. Secreted insulin remained functional. Crucially, beta cells expressing insulin with chromogranin-A signal peptide evaded recognition and killing by autoreactive T cells without inducing ER stress or compromising cellular identity. This approach may offer a targeted alternative to systemic immunosuppression to be used in stem-cell-derived therapies by engineering endogenous insulin signal peptide.