Molecular Mechanisms of Anticancer Activity of N-Glycosides of Indolocarbazoles LCS-1208 and LCS-1269.

Novel indolocarbazole derivatives named LCS were synthesized by our research group. Two of them were selected as the most active anticancer agents in vivo. We studied the mechanisms of anticancer activity in accordance with the previously described effects of indolocarbazoles.

Targeting VE-PTP phosphatase protects the kidney from diabetic injury.

Diabetic nephropathy is a leading cause of end-stage kidney failure. Reduced angiopoietin-TIE2 receptor tyrosine kinase signaling in the vasculature leads to increased vascular permeability, inflammation, and endothelial cell loss and is associated with the development of diabetic complications. Here, we identified a mechanism to explain how TIE2 signaling is attenuated in diabetic animals.

Context-dependent functions of angiopoietin 2 are determined by the endothelial phosphatase VEPTP.

The angiopoietin (ANGPT)-TIE2/TEK signaling pathway is essential for blood and lymphatic vascular homeostasis. ANGPT1 is a potent TIE2 activator, whereas ANGPT2 functions as a context-dependent agonist/antagonist. In disease, ANGPT2-mediated inhibition of TIE2 in blood vessels is linked to vascular leak, inflammation, and metastasis.

ShcA Adaptor Protein Promotes Nephrin Endocytosis and Is Upregulated in Proteinuric Nephropathies.

Nephrin is a key structural component of the podocyte slit diaphragm, and proper expression of nephrin on the cell surface is critical to ensure integrity of the blood filtration barrier. Maintenance of nephrin within this unique cell junction has been proposed to require dynamic phosphorylation events and endocytic recycling, although the molecular mechanisms that control this interplay are poorly understood. Here, we investigated the possibility that the phosphotyrosine adaptor protein ShcA regulates nephrin turnover.

Selective tubular activation of hypoxia-inducible factor-2α has dual effects on renal fibrosis.

Hypoxia-inducible factor (HIF) is a key transcriptional factor in the response to hypoxia. Although the effect of HIF activation in chronic kidney disease (CKD) has been widely evaluated, the results have been inconsistent until now. This study aimed to investigate the effects of HIF-2α activation on renal fibrosis according to the activation timing in inducible tubule-specific transgenic mice with non-diabetic CKD.

Nephrin Tyrosine Phosphorylation Is Required to Stabilize and Restore Podocyte Foot Process Architecture.

Podocytes are specialized epithelial cells of the kidney blood filtration barrier that contribute to permselectivity via a series of interdigitating actin-rich foot processes. Positioned between adjacent projections is a unique cell junction known as the slit diaphragm, which is physically connected to the actin cytoskeleton via the transmembrane protein nephrin. Evidence indicates that tyrosine phosphorylation of the intracellular tail of nephrin initiates signaling events, including recruitment of cytoplasmic adaptor proteins Nck1 and Nck2 that regulate actin cytoskeletal dynamics.

Loss of the podocyte-expressed transcription factor Tcf21/Pod1 results in podocyte differentiation defects and FSGS.

Podocytes are terminally differentiated cells with an elaborate cytoskeleton and are critical components of the glomerular barrier. We identified a bHLH transcription factor, Tcf21, that is highly expressed in developing and mature podocytes. Because conventional Tcf21 knockout mice die in the perinatal period with major cardiopulmonary defects, we generated a conditional Tcf21 knockout mouse to explore the role of this transcription factor in podocytes in vivo.

Vegfa protects the glomerular microvasculature in diabetes.

Vascular endothelial growth factor A (VEGFA) expression is increased in glomeruli in the context of diabetes. Here, we tested the hypothesis that this upregulation of VEGFA protects the glomerular microvasculature in diabetes and that therefore inhibition of VEGFA will accelerate nephropathy. To determine the role of glomerular Vegfa in the development and progression of diabetic nephropathy, we used an inducible Cre-loxP gene-targeting system that enabled genetic deletion of Vegfa selectively from glomerular podocytes of wild-type or diabetic mice.

Biology of anti-angiogenic therapy-induced thrombotic microangiopathy.

Anti-vascular endothelial growth factor (VEGF) agents are an important component in the treatment of many solid tumors. As the indications for these targeted therapies grow, the expected number of patients to receive these drugs will increase exponentially. Despite the great promise, serious toxicities may arise.

Insulin signaling to the glomerular podocyte is critical for normal kidney function.

Diabetic nephropathy (DN) is the leading cause of renal failure in the world. It is characterized by albuminuria and abnormal glomerular function and is considered a hyperglycemic "microvascular" complication of diabetes, implying a primary defect in the endothelium. However, we have previously shown that human podocytes have robust responses to insulin.

Glomerular structure and function require paracrine, not autocrine, VEGF-VEGFR-2 signaling.

VEGF is a potent vascular growth factor produced by podocytes in the developing and mature glomerulus. Specific deletion of VEGF from podocytes causes glomerular abnormalities including profound endothelial cell injury, suggesting that paracrine signaling is critical for maintaining the glomerular filtration barrier (GFB). However, it is not clear whether normal GFB function also requires autocrine VEGF signaling in podocytes.

Nck proteins maintain the adult glomerular filtration barrier.

Within the glomerulus, the scaffolding protein nephrin bridges the actin-rich foot processes that extend from adjacent podocytes to form the slit diaphragm. Mutations affecting a number of slit diaphragm proteins, including nephrin, cause glomerular disease through rearrangement of the actin cytoskeleton and disruption of the filtration barrier. We recently established that the Nck family of Src homology 2 (SH2)/SH3 cytoskeletal adaptor proteins can mediate nephrin-dependent actin reorganization.

Loss of Fat4 disrupts PCP signaling and oriented cell division and leads to cystic kidney disease.

Tissue organization in Drosophila is regulated by the core planar cell polarity (PCP) proteins Frizzled, Dishevelled, Prickle, Van Gogh and Flamingo. Core PCP proteins are conserved in mammals and function in mammalian tissue organization. Recent studies have identified another group of Drosophila PCP proteins, consisting of the protocadherins Fat and Dachsous (Ds) and the transmembrane protein Four-jointed (Fj).

VEGF inhibition and renal thrombotic microangiopathy.

The glomerular microvasculature is particularly susceptible to injury in thrombotic microangiopathy, but the mechanisms by which this occurs are unclear. We report the cases of six patients who were treated with bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF), in whom glomerular disease characteristic of thrombotic microangiopathy developed. To show that local reduction of VEGF within the kidney is sufficient to trigger the pathogenesis of thrombotic microangiopathy, we used conditional gene targeting to delete VEGF from renal podocytes in adult mice; this resulted in a profound thrombotic glomerular injury.

Beta1 integrin expression by podocytes is required to maintain glomerular structural integrity.

Integrins are transmembrane heteromeric receptors that mediate interactions between cells and extracellular matrix (ECM). beta1, the most abundantly expressed integrin subunit, binds at least 12 alpha subunits. beta1 containing integrins are highly expressed in the glomerulus of the kidney; however their role in glomerular morphogenesis and maintenance of glomerular filtration barrier integrity is poorly understood.

Podocytes contribute to the formation of glomerular crescents.

The cellular composition of crescents in glomerular disease is controversial. The role of podocytes in crescent formation has been especially difficult to study because podocytes typically lose their characteristic terminally differentiated phenotype under disease conditions, making them difficult to identify. We reasoned that the intermediate filament protein nestin, a marker of progenitor cells that has recently been identified in podocytes, may allow the investigation of podocyte involvement in glomerular crescents.

Role of the VEGF--a signaling pathway in the glomerulus: evidence for crosstalk between components of the glomerular filtration barrier.

Background/aims: Vascular endothelial growth factor is a major regulator of angiogenesis and vascular permeability [Carmeliet et al.: Nature 1996;380:435-439]. The podocyte, the outermost layer of the glomerular filtration barrier, produces large amounts of VEGF-A.

Nck adaptor proteins link nephrin to the actin cytoskeleton of kidney podocytes.

The glomerular filtration barrier in the kidney is formed in part by a specialized intercellular junction known as the slit diaphragm, which connects adjacent actin-based foot processes of kidney epithelial cells (podocytes). Mutations affecting a number of slit diaphragm proteins, including nephrin (encoded by NPHS1), lead to renal disease owing to disruption of the filtration barrier and rearrangement of the actin cytoskeleton, although the molecular basis for this is unclear. Here we show that nephrin selectively binds the Src homology 2 (SH2)/SH3 domain-containing Nck adaptor proteins, which in turn control the podocyte cytoskeleton in vivo.

Vascular endothelial growth factor a signaling in the podocyte-endothelial compartment is required for mesangial cell migration and survival.

The glomerular filtration barrier separates the blood from the urinary space and consists of two major cell types: podocytes and fenestrated endothelial cells. Mesangial cells sit between the capillary loops and provide structural support. Proliferation and loss of mesangial cells both are central findings in a number of renal diseases, including diabetic nephropathy and mesangiolysis, respectively.

The role of VEGF-A in glomerular development and function.

Purpose Of Review: Vascular endothelial growth factor is a major regulator of blood vessel biology and is highly expressed in presumptive and mature podocytes within the glomerulus. It has long been recognized that dysregulation of this factor occurs in a number of glomerular diseases; however, definitive proof that it plays a pathogenic or developmental role in glomerular biology has remained elusive. This review will summarize some of the recent advances in our understanding of the role(s) of VEGF in these processes.

Glomerular-specific alterations of VEGF-A expression lead to distinct congenital and acquired renal diseases.

Kidney disease affects over 20 million people in the United States alone. Although the causes of renal failure are diverse, the glomerular filtration barrier is often the target of injury. Dysregulation of VEGF expression within the glomerulus has been demonstrated in a wide range of primary and acquired renal diseases, although the significance of these changes is unknown.

A mutant form of the Wilms' tumor suppressor gene WT1 observed in Denys-Drash syndrome interferes with glomerular capillary development.

The Wilms' tumor suppressor gene WT1 encodes a zinc finger protein that is required for urogenital development. In the kidney, WT1 is most highly expressed in glomerular epithelial cells or podocytes, which are an essential component of the filtering system. Human subjects heterozygous for point mutations in the WT1 gene develop renal failure because of the formation of scar tissue within glomeruli.

Glomerular-specific gene excision in vivo.

Podocytes (glomerular visceral epithelial cells) are highly specialized cells that are found in the renal glomerulus and make up a major portion of the filtration barrier between the blood and urinary spaces. Recently, the identification of a number of genes responsible for both autosomal dominant and recessive forms of human nephrotic syndrome has provided insight into a number of molecules responsible for unique features of the podocyte such as the slit diaphragms. Despite these major advances in our understanding of podocyte biology, the function of many genes expressed in the podocyte remains unknown.