The D2D3 form of uPAR acts as an immunotoxin and may cause diabetes and kidney disease.

Soluble urokinase plasminogen activator receptor (suPAR) is a risk factor for kidney diseases. In addition to suPAR, proteolysis of membrane-bound uPAR results in circulating D1 and D2D3 proteins. We showed that when exposed to a high-fat diet, transgenic mice expressing D2D3 protein developed progressive kidney disease marked by microalbuminuria, elevated serum creatinine, and glomerular hypertrophy.

Simultaneous stabilization of actin cytoskeleton in multiple nephron-specific cells protects the kidney from diverse injury.

Chronic kidney diseases and acute kidney injury are mechanistically distinct kidney diseases. While chronic kidney diseases are associated with podocyte injury, acute kidney injury affects renal tubular epithelial cells. Despite these differences, a cardinal feature of both acute and chronic kidney diseases is dysregulated actin cytoskeleton.

Anks1a regulates COPII-mediated anterograde transport of receptor tyrosine kinases critical for tumorigenesis.

ErbB2 signalling, which is amplified by EphA2 binding, is an important therapeutic target for breast cancer. Despite the importance of the EphA2/ErbB2 complex in promoting breast tumorigenesis, the mechanism by which these receptor tyrosine kinases (RTKs) are exported from the endoplasmic reticulum (ER) remains poorly understood. Here we report that the PTB adaptor Anks1a is specifically localized to the ER on its own serine phosphorylation.

Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation.

Rho family GTPases, the prototypical members of which are Cdc42, Rac1, and RhoA, are molecular switches best known for regulating the actin cytoskeleton. In addition to the canonical small GTPases, the large GTPase dynamin has been implicated in regulating the actin cytoskeleton via direct dynamin-actin interactions. The physiologic role of dynamin in regulating the actin cytoskeleton has been linked to the maintenance of the kidney filtration barrier.

Pharmacological targeting of actin-dependent dynamin oligomerization ameliorates chronic kidney disease in diverse animal models.

Dysregulation of the actin cytoskeleton in podocytes represents a common pathway in the pathogenesis of proteinuria across a spectrum of chronic kidney diseases (CKD). The GTPase dynamin has been implicated in the maintenance of cellular architecture in podocytes through its direct interaction with actin. Furthermore, the propensity of dynamin to oligomerize into higher-order structures in an actin-dependent manner and to cross-link actin microfilaments into higher-order structures has been correlated with increased actin polymerization and global organization of the actin cytoskeleton in the cell.

Regulation of dynamin oligomerization in cells: the role of dynamin-actin interactions and its GTPase activity.

Dynamin is a 96-kDa protein that has multiple oligomerization states that influence its GTPase activity. A number of different dynamin effectors, including lipids, actin filaments, and SH3-domain-containing proteins, have been implicated in the regulation of dynamin oligomerization, though their roles in influencing dynamin oligomerization have been studied predominantly in vitro using recombinant proteins. Here, we identify higher order dynamin oligomers such as rings and helices in vitro and in live cells using fluorescence lifetime imaging microscopy (FLIM).

Transient receptor potential channel 6 (TRPC6) protects podocytes during complement-mediated glomerular disease.

Gain-of-function mutations in the calcium channel TRPC6 lead to autosomal dominant focal segmental glomerulosclerosis and podocyte expression of TRPC6 is increased in some acquired human glomerular diseases, particularly in membranous nephropathy. These observations led to the hypothesis that TRPC6 overactivation is deleterious to podocytes through pathological calcium signaling, both in genetic and acquired diseases. Here, we show that the effects of TRPC6 on podocyte function are context-dependent.

Dynamin rings: not just for fission.

The GTPase dynamin has captivated researchers for over two decades, even managing to establish its own research field. Dynamin's allure is partly due to its unusual biochemical properties as well as its essential role in multiple cellular processes, which include the regulation of clathrin-mediated endocytosis and of actin cytoskeleton. On the basis of the classic model, dynamin oligomerization into higher order oligomers such as rings and helices directly executes the final fission reaction in endocytosis, which results in the generation of clathrin-coated vesicles.

CD2AP in mouse and human podocytes controls a proteolytic program that regulates cytoskeletal structure and cellular survival.

Kidney podocytes are highly differentiated epithelial cells that form interdigitating foot processes with bridging slit diaphragms (SDs) that regulate renal ultrafiltration. Podocyte injury results in proteinuric kidney disease, and genetic deletion of SD-associated CD2-associated protein (CD2AP) leads to progressive renal failure in mice and humans. Here, we have shown that CD2AP regulates the TGF-β1-dependent translocation of dendrin from the SD to the nucleus.

Direct dynamin-actin interactions regulate the actin cytoskeleton.

The large GTPase dynamin assembles into higher order structures that are thought to promote endocytosis. Dynamin also regulates the actin cytoskeleton through an unknown, GTPase-dependent mechanism. Here, we identify a highly conserved site in dynamin that binds directly to actin filaments and aligns them into bundles.

Transient activation of the MAP kinase signaling pathway by the forward signaling of EphA4 in PC12 cells.

In the present study, we demonstrate that ephrin-A5 is able to induce a transient increase of MAP kinase activity in PC12 cells. However, the effects of ephrin-A5 on the MAP kinase signaling pathway are about three-fold less than that of EGF. In addition, we demonstrate that EphA4 is the only Eph member expressed in PC12 cells, and that tyrosine phosphorylation induced by ephrin-A5 treatment is consistent with the magnitude and longevity of MAP kinase activation.

Identification of phosphotyrosine binding domain-containing proteins as novel downstream targets of the EphA8 signaling function.

Eph receptors and ephrins have been implicated in a variety of cellular processes, including morphology and motility, because of their ability to modulate intricate signaling networks. Here we show that the phosphotyrosine binding (PTB) domain-containing proteins AIDA-1b and Odin are tightly associated with the EphA8 receptor in response to ligand stimulation. Both AIDA-1b and Odin belong to the ankyrin repeat and sterile alpha motif domain-containing (Anks) protein family.

The EphA8 receptor induces sustained MAP kinase activation to promote neurite outgrowth in neuronal cells.

Recent studies in our laboratory demonstrate that ligand-mediated activation of the EphA8 receptor critically regulates cell adhesion and migration. In this report, we show that the EphA8 receptor induces neurite outgrowth in NG108-15 cells in the absence of ligand stimulation. Using various deletion mutants lacking specific intracytoplasmic regions, we confirm that the tyrosine kinase domain of EphA8 is important for inducing neurite outgrowth.

The p110 gamma PI-3 kinase is required for EphA8-stimulated cell migration.

This study provides evidence that treatment with preclustered ephrin A5-Fc results in a substantial increase in the stability of the p110 gamma PI-3 kinase associated with EphA8, thereby enhancing PI-3 kinase activity and cell migration on a fibronectin substrate. In contrast, co-expression of a lipid kinase-inactive p110 gamma mutant together with EphA8 inhibits ligand-stimulated PI-3 kinase activity and cell migration on a fibronectin substrate, suggesting that the mutant has a dominant negative effect against the endogenous p110 gamma PI-3 kinase. Significantly, the tyrosine kinase activity of EphA8 is not important for either of these processes.

Identification of an enhancer region in the mouse ephA8 locus directing expression to the anterior region of the dorsal mesencephalon.

Eph receptors and ephrins are dynamically expressed in a wide range of regions of the vertebrate during embryogenesis. The dorsal mesencephalon appears to be segmented into two broad regions demarcated by the mutually exclusive expression of EphA receptors and ephrinA ligands. It is of considerable interest to elucidate how these expression domains are established in the development of the mesencephalon.