Pillard, A. | bioRxiv Science

bioRxiv2025

Harmine Selectively Drives Human Beta Cell Differentiation and Function Via Protein Kinase A Pathways

Harmine and other small molecule inhibitors of the kinase DYRK1A induce human beta cells to replicate and regenerate in vitro and in vivo, and are effective at reversing diabetes in animal models. In addition to its beta cell proliferative and regenerative effects, harmine also induces expression of transcription factors and other genes involved in beta cell differentiation and function, exemplified by PDX1, MAFA, NKX6.1, GLP1R, PCSK1 and many others. Harmine also rapidly enhances glucose-stimulated insulin secretion in vitro and in vivo, reversing diabetes within days in diabetic mice transplanted with a marginal mass of human islets. We had assumed that this pro-differentiation or pro-function effect was a common feature of all DYRK1A inhibitors, and was mediated by DYRK1A inhibition. Thus, DYRK1A is a primary target (we refer to it as Target 1) for harmine. Here, to our surprise, we report that the pro-differentiation effect is not a generalized action for all small molecule DYRK1A inhibitors and does not result from DYRK1A interference or genetic silencing. Instead, the prodifferentiation effect is restricted to a small select subset of DYRK1A inhibitors (harmine, 2-2c and 5-IT). Remarkably, the pro-differentiation effect results from the unique ability of these drugs to activate protein kinase A (PKA), a dual mechanism that distinguishes this class from other DYRK1A inhibitors. The beneficial effects of harmine on PKA appear to be indirect, driven by an as yet unidentified, Target 2 in the PKA pathway. These findings make it clear that all DYRK1A inhibitors are not interchangeable, and that those that drive both proliferation and differentiation/function will likely be preferable in human clinical therapeutic settings. They also provide a novel target or roadmap for enhancing human beta cell differentiation in Type 1 and Type 2 diabetes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/692818v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@bd015corg.highwire.dtl.DTLVardef@a46f9borg.highwire.dtl.DTLVardef@19b4f65org.highwire.dtl.DTLVardef@179aa28_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Select DYRK1A Inhibitors Enhance Both Proliferation and Differentiation in Human Pancreatic Beta Cells

The small molecule DYRK1A inhibitor, harmine, induces human beta cell proliferation, expands beta cell mass, enhances expression of beta cell phenotypic genes, and improves human beta cell function in vitro and in vivo. It is unknown whether the "pro-differentiation effect" is a DYRK1A inhibitor class-wide effect. Here we compare multiple commonly studied DYRK1A inhibitors. Harmine, 2-2c and 5-IT increase expression of PDX1, MAFA, NKX6.1, SLC2A2, PCSK1, MAFB, SIX2, SLC2A2, SLC30A8, ENTPD3 in normal and T2D human islets. Unexpectedly, GNF4877, CC-401, INDY, CC-401 and Leucettine fail to induce expression of these essential beta cell molecules. Remarkably, the pro-differentiation effect is independent of DYRK1A inhibition: although silencing DYRK1A induces human beta cell proliferation, it has no effect on differentiation; conversely, harmine treatment enhances beta cell differentiation in DYRK1A-silenced islets. A careful screen of multiple DYRK1A inhibitor kinase candidate targets was unable to identify pro-differentiation pathways. Overall, harmine, 2-2c and 5-IT are unique among DYRK1A inhibitors in their ability to enhance both beta cell proliferation and differentiation. While beta cell proliferation is mediated by DYRK1A inhibition, the pro-differentiation effects of harmine, 2-2c and 5-IT are distinct, and unexplained in mechanistic terms. These considerations have important implications for DYRK1A inhibitor pharmaceutical development.

molecular biology↗