14-3-3 Proteins stabilize actin and vimentin filaments to maintain processes in renal glomerular podocyte.

Abstract

14-3-3 proteins are a ubiquitously expressed family of adaptor proteins. Despite exhibiting high sequence homology, several 14-3-3 isoforms have isoform-specific binding partners and roles. We reported that 14-3-3β interacts with FKBP12 and synaptopodin to maintain the structure of actin fibers in podocytes. However, the precise localization and differential role of 14-3-3 isoforms in kidneys are unclear. Herein, we showed that 14-3-3β in glomeruli was restricted in podocytes, and 14-3-3σ in glomeruli was expressed in podocytes and mesangial cells. Although 14-3-3β was dominantly co-localized with FKBP12 in the foot processes, a part of 14-3-3β was co-localized with Par3 at the slit diaphragm. 14-3-3β interacted with Par3, and FKBP12 bound to 14-3-3β competitively with Par3. Deletion of 14-3-3β enhanced the interaction of Par3 with Par6 in podocytes. Gene silencing for 14-3-3β altered the structure of actin fibers and process formation. 14-3-3β and synaptopodin expression was decreased in podocyte injury models. In contrast, 14-3-3σ in podocytes was expressed in the primary processes. 14-3-3σ interacted with vimentin but not with the actin-associated proteins FKBP12 and synaptopodin. Gene silencing for 14-3-3σ altered the structure of vimentin fibers and process formation. 14-3-3σ and vimentin expression was increased in the early phase of podocyte injury models but was decreased in the late stage. Together, the localization of 14-3-3β at actin cytoskeleton plays a role in maintaining the foot processes and the Par complex in podocytes. In contrast, 14-3-3σ at vimentin cytoskeleton is essential for maintaining primary processes.