The filtration slit diaphragm in the kidney glomerulus is an essential structure formed between podocyte foot processes that serves as a selective barrier during blood filtration. Its molecular composition includes several specialized proteins that maintain the filtration barrier’s integrity and function.

Key Proteins of the Filtration Slit Diaphragm

• Nephrin: A major transmembrane protein that forms the backbone of the slit diaphragm. Mutations in nephrin lead to proteinuria, underscoring its importance.pmc.ncbi.nlm.nih+1

• NEPH1 (Neph-related protein 1): A homologue of nephrin, also a transmembrane protein contributing to slit diaphragm structure and signaling.biorxiv+1

• NEPH2: Another member of the nephrin family found in the slit diaphragm complex, contributing to molecular interactions necessary for filtration.wikipedia+1

Paxillin: A Non-Component

• Paxillin is a cytoskeletal protein mainly involved in focal adhesions and linking the extracellular matrix to the actin cytoskeleton.

• It is not a component of the filtration slit diaphragm.

• Although essential in many cellular processes, paxillin does not participate in the specialized filtration junctions formed by podocytes.

Summary

Conclusion

Among the options provided, Paxillin is not present in the filtration slit diaphragm, unlike Nephrin, NEPH1, and NEPH2, which are key structural and functional components.

Correct Answer: (2) Paxillin