A high-throughput chemical screen reveals that harmine-mediated inhibition of DYRK1A increases human pancreatic beta cell replication

Abstract

Types 1 and 2 diabetes affect some 380 million people worldwide. Both result ultimately from a deficiency of functional pancreatic insulin-producing beta cells. Beta cells proliferate in humans during a brief temporal window beginning around the time of birth, with peak beta cell labeling indices achieving approximately 2% in first year of life1-4. In embryonic life and after early childhood, beta cell replication rates are very low. While beta cell expansion seems an obvious therapeutic approach to beta cell deficiency, adult human beta cells have proven recalcitrant to such efforts1-8. Hence, there remains an urgent need for diabetes therapeutic agents that can induce regeneration and expansion of adult human beta cells in vivo or ex vivo. Here, we report the results of a high-throughput small molecule screen (HTS) revealing a novel class of human beta cell mitogenic compounds, analogues of the small molecule, harmine. We also define dual specificity tyrosine-regulated kinase-1a (DYRK1A) as the likely target of harmine, and the Nuclear Factors of activated T-cells (NFAT) family of transcription factors as likely mediators of human beta cell proliferation as well as beta cell differentiation. These observations suggest that harmine analogues (“harmalogs”) may have unique therapeutic promise for human diabetes therapy. Enhancing potency and beta cell specificity are important future challenges.

High-throughput Functional Genomics Identifies Regulators of Primary Human Beta Cell Proliferation

“…Parenthetically, we did not observe an effect of silencing the CDK inhibitor CDKN1C/p57 (43) perhaps due to insufficient silencing in this context. Recent work indicates that the small molecule harmine, which targets serine/threonine kinases in the CMGC branch of the kinome, can induce 1% of human beta cells to proliferate (44), but its precise target(s) remains unclear. Interestingly, under the same assay conditions Ͼ8% of rodent beta cells proliferate following harmine treatment, supporting the observations that adult human beta cells have evolved additional safeguards against inappropriate proliferation (17)(18)(19)(20).…”

A Pdx-1-Regulated Soluble Factor Activates Rat and Human Islet Cell Proliferation

“…Recently, two groups reported identification of small molecules that stimulate human ␤-cell replication via inhibition of dual-specificity tyrosine kinase-1a (DYRK1A) (27,28). Because the utility of these molecules for clinical intervention remains unknown, development of alternative strategies should continue.…”

Harmine stimulates neurogenesis of human neural cells in vitro

“…Surprisingly, we did not detect changes in proliferation and DYRK2. In cancer studies DYRK1B and DYRK2 have been described as modulators of proliferation 25,26 . In fact, harmine also inhibits DYRK1B and DYRK2 but the efficiency of this inhibition is, respectively, 5-and 50-fold lower in comparison to DYRK1A 18,27,28 .…”