RESUMEN
Endogenous Bone Morphogenetic Protein (BMP) signaling plays a significant role in the kidney's recovery from acute injury and exogenous administration of BMP7 has therapeutic potential in numerous rodent models of renal injury and disease. However, in the healthy kidney endogenous BMP7 ligand is vigorously counteracted by extracellular antagonists such as USAG1 and CHRDL1. Little is known about the degree of BMP signaling and the ligands driving it in the healthy adult kidney. In this study we characterize basal BMP signaling in the healthy tubular nephron, and show that BMP2 is expressed in proximal nephron epithelial cells. Comparative gene profiling of proximal tubule cell responses to BMP2 and BMP7 does not reveal any qualitative difference, suggesting that identical BMP gene targets may be activated in healthy and injured organs. Interestingly, our gene profiling analysis shows that BMP signaling activates a number of Notch regulated transcription factors, including HEY1. As in other biological systems, HEY1 functions as a negative feedback regulator of BMP2 expression in the proximal tubule. In summary, this work reveals endogenous BMP signaling patterns in the healthy human and mouse kidneys, and identifies novel gene targets, some of which are involved in the complex regulation of BMP signaling in the adult kidney.
Asunto(s)
Proteínas Morfogenéticas Óseas/metabolismo , Células Epiteliales/metabolismo , Túbulos Renales Proximales/citología , Receptores Notch/metabolismo , Activación Transcripcional , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Proteínas Morfogenéticas Óseas/genética , Proteínas Morfogenéticas Óseas/farmacología , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Proteínas del Ojo/metabolismo , Perfilación de la Expresión Génica , Genes Reporteros , Humanos , Túbulos Renales Proximales/metabolismo , Luciferasas de Renilla/biosíntesis , Luciferasas de Renilla/genética , Ratones , Proteínas del Tejido Nervioso/metabolismo , Fosforilación , Regiones Promotoras Genéticas , Receptores Notch/genética , Proteínas Recombinantes/metabolismo , Proteínas Smad/metabolismo , Transcripción GenéticaRESUMEN
Follistatin-like 1 (FSTL1) is a secreted protein with homology to both Follistatin and the SPARC/BM40 family of matricellular proteins. In this study, we sought to determine the expression patterns of Fstl1 and its cognate receptor Dip2a in the adult, and to assess the consequences of Fstl1 inactivation on development and homeostasis of the kidney. We find that FSTL1 circulates at high levels in both the human and the mouse and that it is also locally expressed in the loop of Henle in the kidney. To begin to understand the in vivo functions of Fstl1, we generated a mouse mutant using a genetrap approach. The hypomorphic Fstl1 genetrap strain displays a strong reduction in FSTL1 expression at the protein level, but it does not show overt developmental defects. FSTL1 has previously been implicated in diverse disease processes as a regulator of inflammatory cytokine expression, and we therefore evaluated the response of the genetrap strain to cisplatin-mediated acute kidney injury, a disease model with highly cytokine-dependent pathology. We find that although TNF-α and Il6 levels are unchanged relative to wild-type, renal Il-1ß expression is increased in genetrap mice following cisplatin treatment. Furthermore, histopatological analysis, expression of the tissue injury marker Havcr1, and measurement of serum creatinine demonstrate that reduction of Fstl1 expression sensitizes the kidney to acute cisplatin nephrotoxicity, suggesting a role for FSTL1-mediated Il-1ß suppression in protection of the kidney from acute nephrotoxic injury.
Asunto(s)
Lesión Renal Aguda/metabolismo , Proteínas Relacionadas con la Folistatina/fisiología , Interleucina-1beta/biosíntesis , Riñón/metabolismo , Lesión Renal Aguda/inducido químicamente , Adulto , Animales , Cisplatino/toxicidad , Creatinina/sangre , Proteínas Relacionadas con la Folistatina/genética , Células HEK293 , Receptor Celular 1 del Virus de la Hepatitis A , Humanos , Riñón/efectos de los fármacos , Proteínas de la Membrana/biosíntesis , Ratones , Proteínas del Tejido Nervioso/biosíntesis , Proteínas Nucleares , Receptores de Superficie Celular/biosíntesisRESUMEN
Stimulation of the bone morphogenetic protein (BMP) pathway protects the kidney from acute and chronic injury. Numerous regulators in the kidney control BMP signaling, offering many targets for therapeutic manipulation. Here, we screened for modulators of BMP signaling in the ischemia-sensitive S3 segment and found that Chordin-like 1 is expressed in this segment of both the mouse and human nephron. Chordin-like 1 specifically antagonizes BMP7, which is expressed in the neighboring distal nephron, and this depends on the presence of the protein Twisted gastrulation. Upon ischemia-induced degeneration of the S3 segment, we observed a reduction in Chordin-like 1 expression coincident with intense BMP signaling in tubules of the recovering kidney. Restored expression accompanied proximal tubule epithelia redifferentiation, again coincident with decreased BMP signaling. We propose that Chordin-like 1 reduces BMP7 signaling in healthy proximal tubules, and the loss of this activity upon sloughing of injured epithelia promotes BMP7 signaling in repopulating, dedifferentiated epithelia. As regenerating epithelia differentiate, Chordin-like 1 is again expressed, antagonizing BMP7. These data suggest a mechanism for dynamic regulation of renoprotective BMP7 signaling in the S3 segment of the proximal tubule.
Asunto(s)
Proteína Morfogenética Ósea 7/fisiología , Proteínas del Ojo/genética , Isquemia/fisiopatología , Túbulos Renales Proximales/fisiología , Riñón/lesiones , Proteínas del Tejido Nervioso/genética , Proteínas/fisiología , Daño por Reperfusión/fisiopatología , Animales , Proteínas del Ojo/fisiología , Regulación de la Expresión Génica , Humanos , Médula Renal/fisiología , Médula Renal/fisiopatología , Túbulos Renales/lesiones , Túbulos Renales/fisiología , Túbulos Renales Proximales/lesiones , Ratones , Proteínas del Tejido Nervioso/fisiología , Proteínas/genética , RegeneraciónRESUMEN
Follistatin-like 1 (Fstl1) is a distantly related homolog of the Activin and Bone Morphogenetic Protein antagonist Follistatin. Interestingly, this molecule also has homology with the extracellular matrix modifying protein BM-40/SPARC/osteonectin. Previous studies in chick have identified Fstl1 as a regulator of early mesoderm patterning, somitogenesis, myogenesis and neural development. In this study, we determine the developmental expression pattern of Fstl1 in the mouse. We find that Fstl1 is ubiquitously expressed in the early embryo, and that expression becomes regionalized later during development. In the majority of tissues, Fstl1 is strongly expressed in the mesenchymal component and excluded from the epithelium. Notable exceptions include the central nervous system, in which Fstl1 expression is entirely absent with the exception of the choroid plexi and floor plate, the lung, in which Fstl1 expression can be seen in airway epithelia and the kidney, in which collecting ducts and nascent nephron epithelia express the highest levels of Fstl1.
Asunto(s)
Proteínas Relacionadas con la Folistatina/genética , Regulación del Desarrollo de la Expresión Génica , Riñón/embriología , Pulmón/embriología , Organogénesis , Secuencia de Aminoácidos , Animales , Embrión de Mamíferos/metabolismo , Desarrollo Embrionario , Extremidades/embriología , Tracto Gastrointestinal/embriología , Gónadas/embriología , Hibridación in Situ , Riñón/metabolismo , Pulmón/metabolismo , Ratones , Ratones Endogámicos ICR , Datos de Secuencia Molecular , Sistema Nervioso/embriología , Sistema Nervioso/metabolismoRESUMEN
Notch signaling involves proteolytic cleavage of the transmembrane Notch receptor after binding to its transmembrane ligands, Delta or Jagged; and the resultant soluble intracellular domain of Notch stimulates a cascade of transcriptional events. The Delta1 ligand also undergoes proteolytic cleavage upon Notch binding, resulting in the production of a free intracellular domain. We demonstrate that the expression of the intracellular domain of Delta1 results in a non-proliferating senescent-like cell phenotype which is dependent on the expression of the cell cycle inhibitor, p21, and is abolished by co-expression of constitutively active Notch1. These data suggest a new intracellular role for Delta1.