In silico Structural characterization of podocin and assessment of nephrotic syndrome‐associated podocin mutants

Abstract

Nephrotic syndrome (NS) is manifested by hyperproteinuria, hypoalbuminemia, and edema. NPHS2 that encodes podocin was found to have most mutations among the genes that are involved in the pathophysiology of NS. Podocin, an integral membrane protein belonging to stomatin family, is expressed exclusively in podocytes and is localized to slit-diaphragm (SD). Mutations in podocin are known to be associated with steroid-resistant NS and rapid progression to end-stage renal disease, thus signifying its role in maintaining SD integrity and podocyte function. The structural insights of podocin are not known, and the precise mechanism by which podocin contributes to the architecture of SD is yet to be elucidated. In this study, we deduced a model for human podocin, discussed the details of transmembrane localization and intrinsically unstructured regions, and provide an understanding of how podocin interacts with other SD components. Intraprotein interactions were assessed in wild-type podocin and in some of its mutants that are associated with idiopathic NS. Mutations in podocin alter the innate intraprotein interactions affecting the native structure of podocin and its ability to form critical complex with subpodocyte proteins. V C 2016 IUBMB Life, 68(7): [578][579][580][581][582][583][584][585][586][587][588] 2016

Study of A Disintegrin and Metalloproteinase with ThromboSpondin Type 1 Repeats 13 (ADAMTS 13) in Children with Idiopathic Nephrotic Syndrome

“…This is in agreement with U.S. National library of medicine that defined nephrotic syndrome [18] and Mulukala SK, et al [19] who stated that NS is manifested by hyperproteinuria, low total serum protein, hypoalbuminemia and edema. While there is no difference in serum albumin and total serum protein between SSNS and SRNS groups.…”

Structural Features and Oligomeric Nature of Human Podocin Domain

“…This could be due to several reasons including podocin may not be stable outside its native environment, due to the presence of IDRs, or interference of the transmembrane segment with protein expression [5]. We, therefore, cloned and expressed a truncated construct encoding the 126-350 amino acids region of the podocin.…”

“…The intricate structure of the SD is maintained by an array of protein assemblies. Proteins such as podocin, nephrin, CD-2 associated protein (CD2AP), transient receptor potential cation channel subfamily C-member 6 (TRPC6), zonula occludens-1 (ZO-1), and Nephrin-like proteins 1, 2, and 3 (NEPH) interact to form macromolecular complexes and constitute the structure of SD [5][6][7][8].…”

“…Podocin shares 44% homology with stomatin family proteins due to the presence of a highly conserved PHB domain [18]. Indeed, podocin was predicted to share several structural similarities with the stomatin proteins [5,18]. Podocin adapts a hook-like structure with its cytoplasmic N-and C-terminus as it attaches to the inner side of the plasma membrane via a transmembrane domain at 100-125 residues [5,12,19].…”

“…Indeed, podocin was predicted to share several structural similarities with the stomatin proteins [5,18]. Podocin adapts a hook-like structure with its cytoplasmic N-and C-terminus as it attaches to the inner side of the plasma membrane via a transmembrane domain at 100-125 residues [5,12,19]. Structural characterization of stomatin revealed that different truncations of the protein associated with different oligomeric states and that the C-terminus of the protein is crucial for homo-oligomerization [20][21][22].…”