Osteocyte Egln1/Phd2 links oxygen sensing and biomineralization via FGF23

Osteocytes act within a hypoxic environment to control key steps in bone formation.FGF23,a critical phosphate-regulating hormone,is stimulated by low oxygen/iron in acute and chronic diseases,however the molecular mechanisms directing this process remain unclear.Our goal was to identify the osteocyte factors responsible for FGF23 production driven by changes in oxygen/iron utilization.Hypoxia-inducible factor-prolyl hydroxylase inhibitors(HIF-PHI)which stabilize HIF transcription factors,increased Fgf23 in normal mice,as well as in osteocyte-like cells;in mice with conditional osteocyte Fgf23 deletion,circulating i FGF23 was suppressed.An inducible MSC cell line(‘MPC2’)underwent FG-4592 treatment and ATACseq/RNAseq,and demonstrated that differentiated osteocytes significantly increased HIF genomic accessibility versus progenitor cells.Integrative genomics also revealed increased prolyl hydroxylase Egln1(Phd2)chromatin accessibility and expression,which was positively associated with osteocyte differentiation.In mice with chronic kidney disease(CKD),Phd1-3 enzymes were suppressed,consistent with FGF23 upregulation in this model.Conditional loss of Phd2 from osteocytes in vivo resulted in upregulated Fgf23,in line with our findings that the MPC2 cell line lacking Phd2(CRISPR Phd2-KO cells)constitutively activated Fgf23 that was abolished by HIF1αblockade.In vitro,Phd2-KO cells lost iron-mediated suppression of Fgf23 and this activity was not compensated for by Phd1 or-3.In sum,osteocytes become adapted to oxygen/iron sensing during differentiation and are directly sensitive to bioavailable iron.Further,Phd2 is a critical mediator of osteocyte FGF23 production,thus our collective studies may provide new therapeutic targets for skeletal diseases involving disturbed oxygen/iron sensing.

Application of proteomics in environmental science

Proteomics involves the separation of proteins,identification of the amino acid sequence of the interested or target proteins,study of the function of the proteins,modification,structure and ultimate assignments to functional pathways in the cell.The proteomic investigations have contributed greatly to human diseases studies,new drugs discovery researches,and environmental science in recent years.This article provides a review on the development of the main proteomic technologies,including both the gel based and non-gel based technologies,and their applications in environmental science.Proteomic technologies have been utilized in the environmental stresses studies to analyze the induction or reduction of proteins at expression level and identify the target proteins to investigate their function in response to environmental stresses,such as high or low pH,oxidation stress,and toxic chemicals.Such protein responses are also helpful to understand the mechanisms of some cellular activities and the functions of some proteins.