BMPR2 inhibits activin and BMP signaling via wild-type ALK2.

TGF-ß/BMP superfamily ligands require heteromeric complexes of type 1 and 2 receptors for ligand-dependent downstream signaling. Activin A, a TGF-ß superfamily member, inhibits growth of multiple myeloma cells, but the mechanism for this is unknown. We therefore aimed to clarify how activins affect myeloma cell survival. Activin A activates the transcription factors SMAD2/3 through the ALK4 type 1 receptor, but may also activate SMAD1/5/8 through mutated variants of the type 1 receptor ALK2 (also known as ACVR1). We demonstrate that activin A and B activate SMAD1/5/8 in myeloma cells through endogenous wild-type ALK2. Knockdown of the type 2 receptor BMPR2 strongly potentiated activin A- and activin B-induced activation of SMAD1/5/8 and subsequent cell death. Furthermore, activity of BMP6, BMP7 or BMP9, which may also signal via ALK2, was potentiated by knockdown of BMPR2. Similar results were seen in HepG2 liver carcinoma cells. We propose that BMPR2 inhibits ALK2-mediated signaling by preventing ALK2 from oligomerizing with the type 2 receptors ACVR2A and ACVR2B, which are necessary for activation of ALK2 by activins and several BMPs. In conclusion, BMPR2 could be explored as a possible target for therapy in patients with multiple myeloma.This article has an associated First Person interview with the first author of the paper.

Comparison between 8-methoxypsoralen and 5-aminolevulinic acid in killing T cells of photopheresis patients ex vivo.

BACKGROUND AND OBJECTIVE: Extracorporeal photopheresis (ECP), an established modality for cutaneous T-cell lymphoma (CTCL) and graft-versus-host disease, involves ex vivo treatment of isolated leukocytes of a patient with the photosensitizing drug 8-methoxypsoralen (8-MOP) and ultraviolet-A (UV-A) exposure before reinfusion back to the patient. However, 8-MOP binds to both diseased and normal cells and thus kills both types of the cells after UV-A illumination with little selectivity. Clinically, this modality gives only partial response in the majority of treated patients. 5-Aminolevulinic acid (5-ALA), a precursor of the potent photosensitizer protoporphyrin IX (PpIX), has been shown to selectively induce PpIX in activated T lymphocytes (T cells) and could be an alternative for 8-MOP. The objectives of this study were to investigate ex vivo 5-ALA dark toxicity, 5-ALA-induced PpIX production, and photodynamic effect on T cells obtained from clinical ECP patients after the treatment of 5-ALA or 8-MOP plus a built-in certified UV-A source in the commercial Therakos™ Photopheresis System. MATERIALS AND METHODS: Flow cytometry was used to study dark cytotoxic effects of 5-ALA on human leukocytes, to measure the production of 5-ALA-induced PpIX in CD25+ activated T cells from both diluted mononuclear cells and undiluted buffy coat samples of ECP patients and to compare photodynamic effects on CD4+ and CD8+ T cells with 5-ALA/UV-A or 8-MOP/UV-A. RESULTS: No dark toxicity of 5-ALA on the leukocytes of ECP patients was seen at concentrations up to 10 mM for an incubation of up to 20 hours. 5-ALA-induced PpIX was produced more in CD25+ activated T cells than resting T cells in both diluted mononuclear cells and undiluted buffy coat samples, although there was a huge variation of samples from different individual patients. The CD4+ and CD8+ T cells treated with 5-ALA/UV-A were killed more than those treated with 8-MOP/UV-A. CONCLUSION: These results suggest that 5-ALA/UV-A may have the potential for improving the efficacy of ECP. Lasers Surg. Med. 50:469-475, 2018. © 2018 Wiley Periodicals, Inc.

SPBP is a sulforaphane induced transcriptional coactivator of NRF2 regulating expression of the autophagy receptor p62/SQSTM1.

Organisms exposed to oxidative stress respond by orchestrating a stress response to prevent further damage. Intracellular levels of antioxidant agents increase, and damaged components are removed by autophagy induction. The KEAP1-NRF2 signaling pathway is the main pathway responsible for cell defense against oxidative stress and for maintaining the cellular redox balance at physiological levels. Sulforaphane, an isothiocyanate derived from cruciferous vegetables, is a potent inducer of KEAP1-NRF2 signaling and antioxidant response element driven gene expression. In this study, we show that sulforaphane enhances the expression of the transcriptional coregulator SPBP. The expression curve peaks 6-8 hours post stimulation, and parallels the sulforaphane-induced expression of NRF2 and the autophagy receptor protein p62/SQSTM1. Reporter gene assays show that SPBP stimulates the expression of p62/SQSTM1 via ARE elements in the promoter region, and siRNA mediated knock down of SPBP significantly decreases the expression of p62/SQSTM1 and the formation of p62/SQSTM1 bodies in HeLa cells. Furthermore, SPBP siRNA reduces the sulforaphane induced expression of NRF2, and the expression of the autophagy marker protein LC3B. Both these proteins contain ARE-like elements in their promoter regions. Over-expressed SPBP and NRF2 acts synergistically on the p62/SQSTM1 promoter and colocalize in nuclear speckles in HeLa cells. Collectively, these results suggest that SPBP is a coactivator of NRF2, and hence may be important for securing enhanced and sustained expression of NRF2 induced genes such as proteins involved in selective autophagy.