Defining the role of ADGRF5: Insights into kidney health and function

The Glomerulus, the main filtering unit of the kidney, is a complex network of capillaries – small blood vessels that regulate the movement of ions, water, and metabolites while remaining inaccessible to important macromolecules such as proteins . The selective capillary barrier, known as the glomerular filtration barrier (GFB), consists of three main components: glomerular endothelial cells (GEnCs), the glomerular basement membrane, and podocytes. The GEnC line the capillary wall and are covered with a thin layer of glycoproteins and other carbohydrate-based components.

Adhesion G-protein-coupled receptor F5 (ADGRF5), a transmembrane cell receptor expressed in GEnCs, is involved in influencing the integrity of the GFB, which may play a role in its structure and maintenance of function. To clarify the exact role of ADGRF5 in establishing the integrity of the GFB, a joint research study was carried out by scientists from the Tokyo Institute of Technology (Tokyo Tech) and Kyorin University. Their findings were published in the Journal of the American Society of Nephrology on June 06, 2024.

The researchers led by Associate Professor Nobuhiro Nakamura from the School of Life Science and Technology, Tokyo Tech, Japan, and Professor Miki Nagase from the Department of Anatomy, Kyorin University School of Medicine, Japan, conducted a series of experiments knock and knock. in mouse and human GEnCs first to study the specific role and mechanisms of ADGRF5 in maintaining GFB.

Explaining the motivation behind the current study, Dr. Nakamura shared “During our analysis of heart rate data using the Nephroseq v5 database, we noticed a decrease in the data of ADGRF5 mRNA in the glomeruli of patients with diabetic nephropathy. In addition, there was a good communication between the glomerular ADGRF5 expression and glomerular filtration rate.”

At first, the researchers observed the specific expression of ADGRF5 in the endothelial cells that line the wall of the glomerular capillary. In mice with genetic knockouts of ADGRF5, the GFB was involved in damage such as splitting and thickening of the glomerular basement membrane and GEnC detachment. The overall integrity of GFB is severely affected leading to albuminuria – the presence of albumin protein in the urine.

Also, erasing and knocking is ADGRF5 fat in mouse and human GEnCs, respectively, showed changes in the expression of genes important for maintaining the integrity of the GFB. Specifically, knock/knock down d ADGRF5 significantly reduced type IV collagens (Col4a3 and Col4a4) contains GFB and affects GFB permselectivity. In addition, Krüppel-like factor 2 (KLF2), a mechanical transcription factor that regulates endothelial cell function, was found to be up-regulated.

Together, their findings confirm the important functions of ADGRF5 in maintaining the integrity of the GFB. Emphasizing the impact of the research project, said Dr. Nakamura, “This study reveals a new way to maintain GFB. The information on the role of ADGRF5 helps to understand glomerular disorders and has a great contribution to the progress of research in the future.”

The discovery of new functions of the ADGRF5 receptor holds promise for the treatment of chronic glomerular filtration disorders, especially proteinuria.

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