RESUMO
Inflammatory bowel disease (IBD) affects 1.5-3.0 million people in the United States. IBD is genetically determined and many common risk alleles have been identified. Yet, a large proportion of genetic predisposition remains unexplained. In this study, we report the identification of an ultr arare missense variant (NM_006998.3:c.230G > A;p.Arg77His) in the SCGN gene causing Mendelian early-onset ulcerative colitis. SCGN encodes a calcium sensor that is exclusively expressed in neuroendocrine lineages, including enteroendocrine cells and gut neurons. SCGN interacts with the SNARE complex, which is required for vesicle fusion with the plasma membrane. We show that the SCGN mutation identified impacted the localization of the SNARE complex partner, SNAP25, leading to impaired hormone release. Finally, we show that mouse models of Scgn deficiency recapitulate impaired hormone release and susceptibility to DSS-induced colitis. Altogether, these studies demonstrate that functional deficiency in SCGN can result in intestinal inflammation and implicates the neuroendocrine cellular compartment in IBD.
Assuntos
Colite Ulcerativa/genética , Predisposição Genética para Doença , Secretagoginas/deficiência , Animais , Membrana Celular/metabolismo , Vesículas Citoplasmáticas/metabolismo , Modelos Animais de Doenças , Humanos , Fusão de Membrana , Camundongos , Mutação de Sentido Incorreto , Transporte Proteico , Proteínas SNARE/metabolismo , Secretagoginas/genética , Proteína 25 Associada a Sinaptossoma/metabolismoRESUMO
Pain signals are transmitted by multisynaptic glutamatergic pathways. Their first synapse between primary nociceptors and excitatory spinal interneurons gates the sensory load. In this pathway, glutamate release is orchestrated by Ca2+-sensor proteins, with N-terminal EF-hand Ca2+-binding protein 2 (NECAB2) being particular abundant. However, neither the importance of NECAB2+ neuronal contingents in dorsal root ganglia (DRGs) and spinal cord nor the function determination by NECAB2 has been defined. A combination of histochemical analyses and single-cell RNA-sequencing showed NECAB2 in small- and medium-sized C- and Aδ D-hair low-threshold mechanoreceptors in DRGs, as well as in protein kinase C γ excitatory spinal interneurons. NECAB2 was downregulated by peripheral nerve injury, leading to the hypothesis that NECAB2 loss of function could limit pain sensation. Indeed, Necab2-/- mice reached a pain-free state significantly faster after peripheral inflammation than did WT littermates. Genetic access to transiently activated neurons revealed that a mediodorsal cohort of NECAB2+ neurons mediates inflammatory pain in the mouse spinal dorsal horn. Here, besides dampening excitatory transmission in spinal interneurons, NECAB2 limited pronociceptive brain-derived neurotrophic factor (BDNF) release from sensory afferents. Hoxb8-dependent reinstatement of NECAB2 expression in Necab2-/- mice then demonstrated that spinal and DRG NECAB2 alone could control inflammation-induced sensory hypersensitivity. Overall, we identify NECAB2 as a critical component of pronociceptive pain signaling, whose inactivation offers substantial pain relief.
Assuntos
Proteínas de Ligação ao Cálcio/fisiologia , Proteínas do Olho/fisiologia , Hiperalgesia/etiologia , Hiperalgesia/fisiopatologia , Dor/etiologia , Dor/fisiopatologia , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Proteínas de Ligação ao Cálcio/deficiência , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Regulação para Baixo , Proteínas do Olho/genética , Feminino , Gânglios Espinais/fisiopatologia , Hiperalgesia/genética , Inflamação/fisiopatologia , Interneurônios/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Nociceptores/fisiologia , Dor/genética , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/fisiopatologia , Secretagoginas/deficiência , Secretagoginas/genética , Secretagoginas/metabolismo , Medula Espinal/fisiopatologia , Corno Dorsal da Medula Espinal/fisiopatologiaRESUMO
Ca2+-sensor proteins are generally implicated in insulin release through SNARE interactions. Here, secretagogin, whose expression in human pancreatic islets correlates with their insulin content and the incidence of type 2 diabetes, is shown to orchestrate an unexpectedly distinct mechanism. Single-cell RNA-seq reveals retained expression of the TRP family members in ß-cells from diabetic donors. Amongst these, pharmacological probing identifies Ca2+-permeable transient receptor potential vanilloid type 1 channels (TRPV1) as potent inducers of secretagogin expression through recruitment of Sp1 transcription factors. Accordingly, agonist stimulation of TRPV1s fails to rescue insulin release from pancreatic islets of glucose intolerant secretagogin knock-out(-/-) mice. However, instead of merely impinging on the SNARE machinery, reduced insulin availability in secretagogin-/- mice is due to ß-cell loss, which is underpinned by the collapse of protein folding and deregulation of secretagogin-dependent USP9X deubiquitinase activity. Therefore, and considering the desensitization of TRPV1s in diabetic pancreata, a TRPV1-to-secretagogin regulatory axis seems critical to maintain the structural integrity and signal competence of ß-cells.
