Differential effects of inhibition of bone morphogenic protein (BMP) signalling on T-cell activation and differentiation

Bone morphogenetic proteins (BMPs) are involved in patterning and cellular fate in various organs including the thymus. However, the redundancy of BMPs and their receptors have made it difficult to analyse their physiological roles. Here, we investigated the role of BMP signalling in peripheral CD4+ T cells by analysing the effects of an inhibitor of BMP signalling, dorsomorphin. Dorsomorphin suppressed phosphorylation of SMAD1/5/8, suggesting that BMP signalling naturally occurs in T cells. At high doses, dorsomorphin suppressed proliferation of T cells in a dose-dependent manner, inducing G1 arrest. Also, dorsomorphin suppressed Th17 and induced Treg-cell differentiation, while preserving Th2 differentiation. Dorsomorphin efficiently suppressed IL-2 production even at low doses in mouse CD4+ T cells, suggesting that the BMP-Smad signalling physiologically regulates IL-2 transcription in these cells. In addition, recombinant BMP2 induced a dose-dependent multiphasic pattern of IL-2 production, while Noggin suppressed IL-2 production at higher doses in Jurkat cells. Notably, BMP signalling controlled the phosphorylation of RUNX1, revealing the molecular nature of its effect. Collectively, we describe multiple effects of dorsomorphin and Noggin on T-cell activation and differentiation, demonstrating a physiological role for BMP signalling in these processes.