Nephrotic syndrome - scarb2 associated

Definition

Nephrotic syndrome attributed to mutation(s) in the scarb2 gene.

Other names

Action myoclonus–renal failure (AMRF) syndrome

The SCARB2 gene

The SCARB2 gene(scavenger receptor class B member 2) provides instructions for making a protein called lysosomal integral membrane protein-2 (LIMP-2).

Function of LIMP-2

• This protein is primarily found in the membrane of cellular structures called lysosomes, where it attaches to an enzyme called beta-glucocerebrosidase and transports it to the lysosome.
• In lysosomes, beta-glucocerebrosidase breaks down a fatty substance called glucocerebroside.
• The LIMP-2 protein remains in the lysosomal membrane after transporting beta-glucocerebrosidase and is important for the stability of these structures.

Pathophysiology

At least 20 mutations in the SCARB2 gene have been associated with action myoclonus–renal failure (AMRF) syndrome.

Symptoms

It causes episodes of involuntary muscle jerking or muscle twitching, particularly when trying to make intentional movements (action myoclonus). Another common feature of AMRF syndrome is kidney (renal) disease.

Mechanism

SCARB2 gene mutations associated with AMRF syndrome lead to production of an altered LIMP-2 protein that is stuck in the endoplasmic reticulum and cannot get to the lysosome. As a result, the movement of beta-glucocerebrosidase to lysosomes is impaired. It is thought that a shortage of beta-glucocerebrosidase in these structures contributes to the signs and symptoms of AMRF syndrome, although the mechanism is unclear.

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Further reading

• Genetic causes of proteinuria and nephrotic syndrome: Impact on podocyte pathobiology
• Genetics of hereditary nephrotic syndrome: a clinical review
• Genetic Basis of Steroid Resistant Nephrotic Syndrome
• Familiar forms of nephrotic syndrome
• A Single-Gene Cause in 29.5% of Cases of Steroid-Resistant Nephrotic Syndrome

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