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Pancreas lineage allocation and specification are regulated by sphingosine-1-phosphate signalling.

ABSTRACT: During development, progenitor expansion, lineage allocation, and implementation of differentiation programs need to be tightly coordinated so that different cell types are generated in the correct numbers for appropriate tissue size and function. Pancreatic dysfunction results in some of the most debilitating and fatal diseases, including pancreatic cancer and diabetes. Several transcription factors regulating pancreas lineage specification have been identified, and Notch signalling has been implicated in lineage allocation, but it remains unclear how these processes are coordinated. Using a combination of genetic approaches, organotypic cultures of embryonic pancreata, and genomics, we found that sphingosine-1-phosphate (S1p), signalling through the G protein coupled receptor (GPCR) S1pr2, plays a key role in pancreas development linking lineage allocation and specification. S1pr2 signalling promotes progenitor survival as well as acinar and endocrine specification. S1pr2-mediated stabilisation of the yes-associated protein (YAP) is essential for endocrine specification, thus linking a regulator of progenitor growth with specification. YAP stabilisation and endocrine cell specification rely on Gαi subunits, revealing an unexpected specificity of selected GPCR intracellular signalling components. Finally, we found that S1pr2 signalling posttranscriptionally attenuates Notch signalling levels, thus regulating lineage allocation. Both S1pr2-mediated YAP stabilisation and Notch attenuation are necessary for the specification of the endocrine lineage. These findings identify S1p signalling as a novel key pathway coordinating cell survival, lineage allocation, and specification and linking these processes by regulating YAP levels and Notch signalling. Understanding lineage allocation and specification in the pancreas will shed light in the origins of pancreatic diseases and may suggest novel therapeutic approaches.

SUBMITTER: Serafimidis I

PROVIDER: S-EPMC5331964 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Sphingosine 1-phosphate is formed in cells in response to diverse stimuli, including growth factors, cytokines, G-protein-coupled receptor agonists, antigen, etc. Its production is catalysed by sphingosine kinase, while degradation is either via cleavage to produce palmitaldehyde and phosphoethanolamine or by dephosphorylation. In this review we discuss the most recent advances in our understanding of the role of the enzymes involved in metabolism of this lysolipid. Sphingosine 1-phosphate can also bind to members of the endothelial differentiation gene (EDG) G-protein-coupled receptor family [namely EDG1, EDG3, EDG5 (also known as H218 or AGR16), EDG6 and EDG8] to elicit biological responses. These receptors are coupled differentially via G(i), G(q), G(12/13) and Rho to multiple effector systems, including adenylate cyclase, phospholipases C and D, extracellular-signal-regulated kinase, c-Jun N-terminal kinase, p38 mitogen-activated protein kinase and non-receptor tyrosine kinases. These signalling pathways are linked to transcription factor activation, cytoskeletal proteins, adhesion molecule expression, caspase activities, etc. Therefore sphingosine 1-phosphate can affect diverse biological responses, including mitogenesis, differentiation, migration and apoptosis, via receptor-dependent mechanisms. Additionally, sphingosine 1-phosphate has been proposed to play an intracellular role, for example in Ca(2+) mobilization, activation of non-receptor tyrosine kinases, inhibition of caspases, etc. We review the evidence for both intracellular and extracellular actions, and extensively discuss future approaches that will ultimately resolve the question of dual action. Certainly, sphingosine 1-phosphate will prove to be unique if it elicits both extra- and intra-cellular actions. Finally, we review the evidence that implicates sphingosine 1-phosphate in pathophysiological disease states, such as cancer, angiogenesis and inflammation. Thus there is a need for the development of new therapeutic compounds, such as receptor antagonists. However, identification of the most suitable targets for drug intervention requires a full understanding of the signalling and action profile of this lysosphingolipid. This article describes where the research field is in relation to achieving this aim.

Project description:Because sphingosine 1-phosphate (S1P) is a potent stimulator of angiogenesis, we hypothesized that the S1P pathway is activated to stimulate endometrial/placental angiogenesis during pregnancy. We initially localized S1P signaling pathway members in the gravid and nongravid uterine horns of unilaterally pregnant ewes. Sphingosine kinase-1 expression was greater in gravid compared to nongravid horns. In situ hybridization revealed elevated expression of sphingosine 1-phosphate phosphatase (SGPP1) in gravid interplacentomal endometrial stroma on Days 20 and 40 compared to the nongravid uterine horn, but expression increased in endometrium of the nongravid uterine horn between Days 40 and 120. SGPP1 expression increased in placentomes late in gestation. Sphingosine 1-phosphate lyase mRNA was modestly expressed at Day 20 and then decreased. In contrast, sphingosine 1-phosphate receptor 1 (S1PR1) mRNA increased in endometrium and caruncular stroma of the gravid uterine horn. Treatment with FTY720 and VPC23019, S1P receptor antagonists, blocked human and ovine endothelial cell invasion using an in vitro model of sprouting angiogenesis. Knockdown of S1PR1 with siRNA reduced invasion responses as well. We previously reported that delta-like 4 (DLL4) and A disintegrin and metalloproteinase with thrombospondin-like repeats 1 (ADAMTS1) participate in endothelial cell invasion stimulated by S1P and growth factors in vitro, and thus investigated whether their expression correlated with areas undergoing angiogenesis in vivo. DLL4 expression was similar to S1PR1, while ADAMTS1 mRNA was expressed by endometria of both nongravid and gravid horns, as well as conceptus and placentomes. These results establish that S1P signaling pathway members and S1P- and growth factor-regulated genes are prominent in uterine and placental tissue and in some cases are correlated with areas undergoing angiogenesis. Thus, S1P signaling may be crucial for proper fetal-placental development.

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Pancreas lineage allocation and specification are regulated by sphingosine-1-phosphate signalling.

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