Pathogenic uromodulin mutations result in premature intracellular polymerization

Area of Science:

• Nephrology
• Molecular Biology
• Biochemistry

Background:

• Uromodulin (UMOD) is the most abundant protein in urine and is crucial for kidney function.
• Mutations in the UMOD gene are linked to several inherited renal diseases.
• Understanding UMOD's intracellular processing is key to elucidating disease mechanisms.

Purpose of the Study:

• To investigate the intracellular processing and trafficking of wild-type uromodulin and disease-associated mutants.
• To determine the structural characteristics of intracellular mutant uromodulin.
• To explore the link between intracellular protein behavior and renal disease pathology.

Main Methods:

• Transfection of tsA 201 cells with wild-type and mutant UMOD constructs (p.V93_G97del/ins AASC, C155R, C150S).
• Analysis of protein localization and processing via cell-based assays.
• Examination of intracellular protein structures using atomic force microscopy.
• Review of renal biopsy from a patient with C155R mutation.

Main Results:

• Wild-type uromodulin was efficiently trafficked to the cell surface.
• Mutant uromodulin variants (p.V93_G97del/ins AASC, C155R, C150S) showed partial intracellular retention and incomplete processing.
• Intracellular mutant uromodulin proteins exhibited fibrillar structures resembling urinary uromodulin.
• Renal biopsy confirmed intracellular protein accumulation in a patient with the C155R mutation.

Conclusions:

• Aberrant intracellular processing and polymerization of uromodulin mutants occur.
• Premature intracellular polymerization of uromodulin is a likely driver of renal disease pathogenesis.
• These findings provide insights into the molecular mechanisms of uromodulin-associated kidney disorders.