Molecular Mechanisms of Albumin Trafficking in Podocytes
Principal Investigator: Judith T Blaine
Abstract: DESCRIPTION (provided by applicant): Chronic kidney disease (CKD) is a national health problem that affects ~ 39 million Americans. Progression of chronic kidney disease to end stage kidney disease is associated with considerable cardiovascular morbidity and mortality. Albuminuria is one of the key features of chronic kidney disease and a marker of CKD progression. The mechanisms of albumin excretion in the urine are poorly understood. In normal subjects, resistance to albumin excretion in the urine is mediated by an intact glomerular filtration barrier which is comprised of glomerular endothelial cells, the glomerular basement membrane, podocyte foot processes and the sub-podocyte space. In chronic kidney disease and other proteinuric states these barriers are disturbed allowing significant quantities of albumin to escape into the urine. Podocytes can take up albumin but the mechanisms of endocytosis in podocytes are not known. Our overall hypothesis is that healthy podocytes endocytose albumin in a polarized and receptor-mediated manner and that in albuminuric states the uptake and disposal of albumin is overwhelmed, leading to toxicity to the podocyte and increased podocyte death. In Specific Aim 1 we will examine albumin endocytosis and degradation in healthy podocytes. Specifically, we will test the hypothesis that albumin endocytosis occurs at the basal cell membrane and is mediated by megalin and that albumin degradation occurs in the lysosome. In Specific Aim 2 we will examine albumin handling in podocytes in the nephrotic state. We hypothesize that in heavy albuminuria albumin uptake is disordered and albumin degradation is impaired. Specifically, we will examine whether in nephrotic states albumin uptake is no longer confined to the basal membrane and whether albumin overload leads to activation of lysosomal enzymes and disruption of lysosomal integrity. To test our hypotheses we will use a combination of molecular biology and advanced imaging techniques in cultured human podocytes and will extend our findings to a mouse model of nephrotic syndrome. Our proposal is novel in that it proposes a mechanistic link between impaired albumin handling and podocyte death. Increased podocyte loss due to albumin toxicity may be an important factor in kidney disease progression since podocytes are terminally differentiated cells with low regenerative capacity and podocyte loss is strongly correlated with progressive kidney failure. In addition, this proposal will lay the foundation for an R01 submission. Determination of the mechanisms of albumin uptake and disposal in normal podocytes will allow comparison of these mechanisms in APOL1 risk allele podocytes. We hypothesize that albumin acts as a "second hit" in APOL1 mutant podocytes that have a genetic predisposition to accelerated loss. In addition, identification of the pathways necessary for albumin uptake may allow for future intervention studies that limit albumin uptake by podocytes in heavy albuminuria, thereby decreasing podocyte death and slowing kidney disease progression.
Funding Period: 2013-07-01 - 2015-06-30
more information: NIH RePORT
- Human podocytes perform polarized, caveolae-dependent albumin endocytosisEvgenia Dobrinskikh
Div of Renal Diseases and Hypertension, 12700 E 19th Ave, C281, Aurora, CO 80045
Am J Physiol Renal Physiol 306:F941-51. 2014..These studies confirm the ability of podocytes to endocytose albumin and provide mechanistic insight into cellular mechanisms and fates of albumin handling in podocytes...
- KIM-1, microparticles and diabetic tubular injuryXueying Zhao; Fiscal Year: 2013..Our studies will also shed light on KIM-1/KIM-MPs as attractive targets for kidney disease management. ..
- The Virtual Physiological Rat ProjectDaniel A Beard; Fiscal Year: 2013..This proposal targets the grand challenge of understanding complex multi-faceted disease phenotypes through experiments and simulations that capture the complex genotype-environment-phenotype relationship. ..
- STUDIES OF ORGAN TRANSPLANTATION IN ANIMALS AND MANArthur J Matas; Fiscal Year: 2013..2. To maximize rehabilitation. The focus here is on minimizing complications and maximizing quality of life. ..
- North American Mitochondrial Disease Consortium (NAMDC)JOHN L THOMPSON; Fiscal Year: 2013....
- Innate/Adaptive Immune Interactions in Gut InflammationSergio A Lira; Fiscal Year: 2013..Overall the focus and interactive nature of the program (20 joint publications in 4 years, 3 additional NIH grants on related areas) provide a solid basis for a productive outcome. ..
- Vitamin D Deficiency in Glomerular DiseaseMichelle Denburg; Fiscal Year: 2013....
- Porphyria Rare Disease Clinical Research Consortium (RDCRC)Robert J Desnick; Fiscal Year: 2013..Kushner, MD, Professor of Medicine at UoU. Additional affiliate centers will be included over time as funding permits, including support from other grants and philanthropic sources. ..
- Center for Excellence in Diabetes and Obesity ResearchARUNI BHATNAGAR BHATNAGAR; Fiscal Year: 2013..Continued support to the Center will strengthen the infrastructure of biomedical research at the University of Louisville and will positively impact the field of diabete and obesity research worldwide. ..
- The Role of Endocytosis and Actin Regulation in PodocytesShuta Ishibe; Fiscal Year: 2013..By completing these aims, we will have an opportunity to further expand our knowledge of endocytic pathways vital for podocyte homeostasis. ..
- Role of Eicosanoids in Renal FunctionNANCY JOAN BROWN; Fiscal Year: 2013..These are needed for the development of meaningful approaches for: a) the unequivocal definition of human pathophysiological significance, and b) future pharmacological targeting, and clinical diagnosis and intervention. ..
- Role of myosin 1e in podocyte biology and renal filtrationMira Krendel; Fiscal Year: 2013..Aim 3. Test the ability of myo1e mutants to rescue the defects in glomerular filtration in mice lacking myo1e. ..
- Expanding Excellence in Developmental Biology in OklahomaLinda F Thompson; Fiscal Year: 2013..abstract_text> ..
- IPF Fibroblast PhenotypeCraig A Henke; Fiscal Year: 2013..A major objective of this Program Project is to inform decisions of the IPF Clinical Network by providing information that can be translated into novel therapeutic strategies for IPF. ..
- Glomerular Capillaries-- Normal and PathologicMarilyn Gist Farquhar; Fiscal Year: 2013..abstract_text> ..
- Linking the physical and chemical characteristics of Qdots to their toxicityTERRANCE JAMES KAVANAGH; Fiscal Year: 2013..These advances can then be used in safe design and manufacturing of nanomaterials so as to maximize their utility for many applications. ..
- Beta-catenin Signaling and Podocyte DysfunctionYouhua Liu; Fiscal Year: 2013..The proposed studies may potentially have wide implications in designing future therapeutic regimens for the treatments of proteinuric kidney diseases. ..
- KIDNEY INJURY MOLECULE-1 IN EPITHELIAL REPAIRJOSEPH VINCENT BONVENTRE; Fiscal Year: 2013....
- Regulatory Mechanisms In Intestinal MotilityKenton M Sanders; Fiscal Year: 2013..The investigative team is highly synergistic and collaborative, and the PPG has a long track-record of productivity and novel discovery ..
- NITRIC OXIDE SYNTHASE IN THE JUXTAGLOMERULAR APPARATUSChristopher S Wilcox; Fiscal Year: 2013..abstract_text> ..
- BIOLOGY OF NEUROENDOCRINE PEPTIDESMarc R Montminy; Fiscal Year: 2013..Specifying the contributions of the CRF family of ligands and receptors to the maintenance of homeostasis and to stress-linked allostasis may improve our ability to manage diseases, including mood and metabolic disorders ..
- Genetics of Renal End Organ Damage in HypertensionMichael R Garrett; Fiscal Year: 2013..abstract_text> ..
- Protein Handling By Renal Proximal Tubule Epithelial CellsNicholas Ferrell; Fiscal Year: 2013....
- Role of Focal Adhesion Kinase (FAK) in Nephrosis and NephritisShuta Ishibe; Fiscal Year: 2013..The goal of the proposal is to define the mechanisms that are involved during kidney injury and to utilize inhibitors that antagonize against the offending agent(s) responsible for disease progression. ..
- COBRE in Lipidomics and PathobiologyBesim Ogretmen; Fiscal Year: 2013....