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Shuta Ishibe, MD

Professor of Medicine (Nephrology)
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Additional Titles

Director, Undergraduate Summer Research Program for Nephrology

Director, Research Fellowship

Director for Educational Enrichment, George M. O'Brien Center, Nephrology

Section Chief (Interim), Nephrology

About

Titles

Professor of Medicine (Nephrology)

Director, Undergraduate Summer Research Program for Nephrology; Director, Research Fellowship; Director for Educational Enrichment, George M. O'Brien Center, Nephrology; Section Chief (Interim), Nephrology

Biography

My major area of research interest include the endocytic process and matrix regulation in podocytes.


Our laboratory has identified the critical role of the clathrin coated endocytic processes in the development and maintenance of podocytes. In-vivo animal models with conventional or conditional ablation of genes implicated for endocytosis, such as synaptojanin, endophilin, and dynamin develop severe proteinuria and foot process effacement. By utilizing fluorescently tagged proteins, we have visualized these proteins along with genes implicated to cause human nephrotic syndrome (CD2AP, Myo1e, Nephrin) lie at the interface of endocytosis and actin cytoskeleton. One of the major goals of the laboratory is investigating and further understanding the critical factors that are being endocytosed in podocytes. We have also sought to examine the role of cell matrix interactions by providing mechanistic insight on focal adhesion proteins and integrins, which govern podocyte cell adhesion and movement during health and disease states, using mouse genetic models of disease.

Appointments

Education & Training

Resident
Parkland Memorial Hospital (2000)
Internship
Parkland Memorial Hospital (1998)
MD
University of Texas Southwestern Medical School (1997)
BA
Rice University (1993)

Research

Overview

My research in Dr. Lloyd Cantley’s laboratory (Professor of Internal Medicine at Yale University) had focused on hepatocyte growth factor (HGF), a secreted protein that plays important roles in epithelial morphogenesis, mitogenesis, and motogenesis. We made the novel discovery that paxillin functions as a scaffolding protein that regulates the HGF-dependent activation of ERK at focal adhesions. In a follow-up study, we demonstrated that paxillin itself is a substrate to ERK-dependent phosphorylation, which recruits FAK and Rac and is necessary for HGF-dependent tubulogenesis. These findings were published as two first-authored papers in Molecular Cell and are important because they elucidate the mechanism by which HGF regulates focal adhesion turnover, which is essential for cell spreading and morphogenesis. More generally, they explain how compartmentalization of MAP kinase signaling is achieved through local activation on scaffolding proteins, such as paxillin. In a third study we observed that during in vitro tubulogenesis, the cells located in the middle of the tubules appeared well differentiated whereas cells located at the ends had a mesenchymal appearance. We discovered that cell confluency modulates the responsiveness to HGF through its effects on the activation of Akt and beta-catenin. These findings were published in MCB and are relevant to the mechanism of tubular regeneration after acute kidney injury, which we hypothesize involves HGF-stimulated cell spreading, proliferation, and dedifferentiation

After starting my own laboratory, we have focused on podocytes, the specialized epithelial cells that maintain the glomerular filtration barrier, and are critical targets in proteinuric disorders such as diabetic nephropathy. My current research in podocyte biology is concentrated in two areas.

One interest lies in the further understanding of cell-matrix biology in his study of podocytes. When podocytes are injured, the foot processes undergo a term known as effacement, where the cells collapse losing cell-cell junction proteins resulting in proteinuria. A mechanisms of podocytes undergoing foot process effacement likely requires cell spreading and motility which requires turnover of focal adhesion proteins, which acts as a“glue” to keep cells attached to its matrix. To further address this hypothesis, a key focal adhesion protein, FAK, was conditionally deleted in podocytes taking advantage of mice genetics. Generation of these mice resulted in resistance to proteinuria induced by various injury models. Moreover, as FDA approved FAK inhibitors are available, through collaboration with Novartis Pharmaceuticals, treatment of mice with FAK inhibitors during injury significantly reduced proteinuria and histological kidney injury.

My second interest in podocyte biology is to evaluate the importance of various interacting partners of known human disease causing mutations that result in nephrotic syndrome. Currently, we have identified a network of proteins that bind directly or indirectly to proteins that human genetic studies have implicated to be causal for nephrotic syndrome. Through mice genetics, loss of specific proteins in this network has demonstrated severe proteinuria, and podocyte foot process effacement. Through collaboration with Dr. Pietro De Camilli, we have found that these network of proteins lie at the interface of endocytosis and the actin cytoskeleton and now are in the process of expanding our understanding by determining critical factors that are being endocytosed in the podocytes. Hopefully these fundamental findings will lead to therapeutic targets in the treatment of nephrotic syndrome in the future.

The future directions of my lab are to further understand cell-matrix biology and endocytosis in podocytes by using mice genetic models of disease. Moreover, we are in the process of obtaining human samples to discover novel disease mutations, which may lead to further understanding of disease processes leading to nephrotic syndrome.

Analyzing the role of podocyte cell-matrix interactions

Analyzing the role of podocyte endocytosis

Medical Subject Headings (MeSH)

Glomerular Filtration Barrier; Nephrology; Nephrotic Syndrome; Physiology; Podocytes; Proteinuria

Research at a Glance

Yale Co-Authors

Frequent collaborators of Shuta Ishibe's published research.

Publications

2024

2023

2022

Academic Achievements & Community Involvement

  • activity

    American Society for Clinical Investigation

  • activity

    Nature Medicine, The Journal of Clinical Investigation, Journal of American Society of Nephrology, Kidney International, American Journal of Physiology, Molecular and Cellular Biology, Proceedings of the National Academy of Sciences, PLOS-One, FASEB

  • activity

    Kidney 360

  • activity

    Yale Scholar Awards

  • activity

    NIH / NIDDK PBKD

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