RNA-seq analysis of glycosylation related gene expression in STZ-induced diabetic rat kidney inner medulla.
The UT-A1 urea transporter is crucial to the kidney's ability to generate concentrated urine. Native UT-A1 from kidney inner medulla (IM) is a heavily glycosylated protein with two glycosylation forms of 97 and 117 kDa. In diabetes, UT-A1 protein abundance, particularly the 117 kD isoform, is significantly increased corresponding to an increased urea permeability in perfused IM collecting ducts, which plays an important role in preventing the osmotic diuresis caused by glucosuria. However, how the glycan carbohydrate structure change and the glycan related enzymes regulate kidney urea transport activity, particularly under diabetic condition, is largely unknown. In this study, using sugar-specific binding lectins, we found that the carbohydrate structure of UT-A1 is changed with increased amounts of sialic acid, fucose, and increased glycan branching under diabetic conditions. These changes were accompanied by altered UT-A1 association with the galectin proteins, β-galactoside glycan binding proteins. To explore the molecular basis of the alterations of glycan structures, the highly sensitive next generation sequencing (NGS) technology, Illumina RNA-seq, was employed to analyze genes involved in the process of UT-A1 glycosylation using streptozotocin (STZ)-induced diabetic rat kidney. Differential gene expression analysis combining with quantitative PCR revealed that expression of a number of important glycosylation related genes were changed under diabetic conditions. These genes include the glycosyltransferase genes Mgat4a, the sialylation enzymes St3gal1 and St3gal4 and glycan binding protein galectin-3, -5, -8, and -9. In contrast, although highly expressed in kidney IM, the glycosyltransferase genes Mgat1, Mgat2, and fucosyltransferase Fut8, did not show any changes.


CONCLUSIONS
In diabetes, not only is UT-A1 protein abundance increased but the protein's glycan structure is also significantly changed. UT-A1 protein becomes highly sialylated, fucosylated and branched. Consistently, a number of crucial glycosylation related genes are changed under diabetic conditions. The alteration of these genes may contribute to changes in the UT-A1 glycan structure and therefore modulate kidney urea transport activity and alleviate osmotic diuresis caused by glucosuria in diabetes.
Department of Physiology, Emory University School of Medicine Atlanta, GA, USA ; Department of Cardiology, The Fourth Affiliated Hospital of Harbin Medical University Harbin, China.
Xiaoqian
X
Qian
Department of Physiology, Emory University School of Medicine Atlanta, GA, USA.
Xuechen
X
Li
Renal Division, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA.
Titilayo O
TO
Ilori
Department of Physiology, Emory University School of Medicine Atlanta, GA, USA ; Renal Division, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA.
Janet D
JD
Klein
Renal-Electrolyte Division and Department of Cell Biology and Physiology, Department of Medicine, University of Pittsburgh School of Medicine Pittsburgh, PA, USA.
Rebecca P
RP
Hughey
Bovine Functional Genomics Laboratory, United States Department of Agriculture - Agricultural Research Service Beltsville, MD, USA.
Cong-Jun
CJ
Li
Department of Physiology, Emory University School of Medicine Atlanta, GA, USA.
Abdel A
AA
Alli
Department of Electrical and Computer Engineering, TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University College Station, TX, USA.
Zhengyu
Z
Guo
Department of Electrical and Computer Engineering, TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University College Station, TX, USA.
Peng
P
Yu
Department of Cardiology, The Fourth Affiliated Hospital of Harbin Medical University Harbin, China.
Xiang
X
Song
Department of Physiology, Emory University School of Medicine Atlanta, GA, USA ; Renal Division, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA.
Guangping
G
Chen
Illumina; diabetes; fucosylation; gene expression; sialylation; urinary concentration