2. Soluble CASK – a new factor implicated in recurrent FSGS

The last post left us back to square one in finding the elusive circulating factor responsible for recurrent FSGS. The abstract presented by Dr. Beaudreuil from France presents another target of interest.

Treatment for recurrent FSGS includes immunoadsorption (IA) with protein A columns. The authors compared IA eluates from patients treated for rFSGS to those being treated with IA for other reasons. When comparing the samples using mass spectroscopy they found a molecule — CASK (calcium/calmodulin-dependent serine-threonine kinase) — which was expressed only in the patients with rFSGS. CASK is a molecule found in the slit diaphragm. In vitro they found that recombinant CASK induces structural alterations in podocytes possibly by interacting with CD98. Next they infused CASK into mice. Within 24 hrs the mice displayed proteinuria and foot process alterations. The authors conclude that CASK may be responsible for recurrent FSGS. Although the data sound convincing, larger studies, and studies from different labs will have to confirm these findings. As with the suPAR story it may be too early to believe that we have identified the circulating factor responsible for recurrent FSGS.

Post written by Dr. Vinay Nair, eAJKD Advisory Board member.

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