Cross-Talk between Extracellular S1P/S1P2 and P42/44 MAPK in bcr/abl Positive Chronic Myeloid Leukemia Cells

Objective： BCR/ABL oncoprotein-expression is associated with uncontrolled cell growth. Sphingosine kinase 1 （SPK1） regulates the production of sphingosine 1-phosphate （S1P）, a key lipid signal molecular in cell proliferation and survival. The objective of this study was to elucidate the roles of S1P and its receptors in bcr/abl positive chronic myeloid leukemia （CML） cells. Methods： The expressions of SIP receptors： S1P1, S1P2 and S1P3 in CML cells were detected by RT-PCR. SPK1 expression, activity and extracellular S1P were determined in ECV304 and HL-60 cells which were transfected with bcr/abl gene. To elucidate the relationship between the BCR/ABL, ERK/MAPK （extracellular signal-regulated kinase/mitogen-activated protein kinase）, SPK/S 1P and S 1P/S 1 P2 signal pathways, bcr/abl positive CML cell line K562 was treated with STI571, PD98059, N,N-dimethyl sphingosine （DMS） and JTE-013. Results： Retrovirus-mediated overexpression of bcr/abl gene in ECV304 and HL-60 cells resulted in upregulation of the expression, activity of SPK1 and increase of the secretion of SIP, whereas treatment of STI571 and PD98059 decreased the BCR/ABL-induced S1P secretion. Treatment of DMS reduced S1P secretion and P42/44MAPK phosphorylation. S1P2-selective antagonist JTE-013 could also decrease P42/44MAPK phosphorylation. Conclusion： These results suggest that BCR/ABL up-regulates extracellular sphingosine 1-phosphate through sphingosine kinase 1 and there is cross-talk between SPK1/S1P/S1P2 and P42/44MAPK in bcr/abl positive CML cells.

OTUB1 promotes osteoblastic bone formation through stabilizing FGFR2

Bone homeostasis is maintained by the balance between osteoblastic bone formation and osteoclastic bone resorption.Dysregulation of this process leads to multiple diseases,including osteoporosis.However,the underlying molecular mechanisms are not fully understood.Here,we show that the global and conditional osteoblast knockout of a deubiquitinase Otub1 result in low bone mass and poor bone strength due to defects in osteogenic differentiation and mineralization.Mechanistically,the stability of FGFR2,a crucial regulator of osteogenesis,is maintained by OTUB1.OTUB1 attenuates the E3 ligase SMURF1-mediated FGFR2 ubiquitination by inhibiting SMURF1’s E2 binding.In the absence of OTUB1,FGFR2 is ubiquitinated excessively by SMURF1,followed by lysosomal degradation.Consistently,adeno-associated virus serotype 9(AAV9)-delivered FGFR2 in knee joints rescued the bone mass loss in osteoblast-specific Otub1-deleted mice.Moreover,Otub1 mRNA level was significantly downregulated in bones from osteoporotic mice,and restoring OTUB1 levels through an AAV9-delivered system in ovariectomy-induced osteoporotic mice attenuated osteopenia.Taken together,our results suggest that OTUB1 positively regulates osteogenic differentiation and mineralization in bone homeostasis by controlling FGFR2 stability,which provides an optical therapeutic strategy to alleviate osteoporosis.

The deubiquitinase OTUD1 inhibits colonic inflammation by suppressing RIPK1-mediated NF-κB signaling

The E3 ubiquitin ligase(E3)-mediated ubiquitination and deubiquitinase(DUB)-mediated deubiquitination processes are closely associated with the occurrence and development of colonic inflammation.Ovarian tumor deubiquitinase 1(OTUD1)is involved in immunoregulatory functions linked to infectious diseases.However,the effect of OTUD1 on intestinal immune responses during colonic inflammatory disorders such as inflammatory bowel disease(IBD)remains unclear.Here,we show that loss of OTUD1 in mice contributes to the pathogenesis of dextran sulfate sodium(DSS)-induced colitis via excessive release of proinflammatory cytokines.In addition,bone marrow transplantation experiments revealed that OTUD1 in hematopoietic cells plays a dominant role in protection against colitis.Mechanistically,OTUD1 physically interacts with receptor-interacting serine/threonine-protein kinase 1(RIPK1)and selectively cleaves K63-linked polyubiquitin chains from RIPK1 to inhibit the recruitment of NF-κB essential modulator(NEMO).Moreover,the expression of OTUD1 in mucosa samples from ulcerative colitis(UC)patients was lower than that in mucosa samples from healthy controls.Furthermore,we demonstrate that the UC-associated OTUD1 G430V mutation abolishes the ability of OTUD1 to inhibit RIPK1-mediated NF-κB activation and intestinal inflammation.Taken together,our study unveils a previously unexplored role of OTUD1 in moderating intestinal inflammation by inhibiting RIPK1-mediated NF-κB activation,suggesting that the OTUD1-RIPK1 axis could be a potential target for the treatment of IBD.