Yes-associated Protein (YAP) Promotes Cell Survival by Inhibiting Proapoptotic Dendrin Signaling

Kirk N Campbell,Jenny S Wong,Ritu Gupta,Katsuhiko Asanuma,Marius Sudol,John Cijiang He,Peter Mundel

doi:10.1074/jbc.c113.457390

Abstract

Kidney podocytes are highly specialized terminally differentiated cells that form the final barrier to urinary protein loss. Podocytes are a target for injury by metabolic, autoimmune, hereditary, inflammatory, and other stressors. Persistence of podocyte injury leads to podocyte death and loss, which results in progressive kidney damage and ultimately kidney failure. Dendrin is a dual compartment protein with proapoptotic signaling properties. Nuclear relocation of dendrin in response to glomerular injury promotes podocyte apoptosis. Here we show that Yes-associated protein (YAP), a downstream target of Hippo kinases and an inhibitor of apoptosis, is expressed in the nucleus of podocytes. The WW domains of YAP mediate the interaction with the PPXY motifs of dendrin. This interaction is functionally relevant because YAP binding to dendrin reduces dendrin-dependent, staurosporine-induced apoptosis in co-transfected HEK293 cells. Moreover gene silencing of YAP in podocytes increases adriamycin-induced podocyte apoptosis. It also increases staurosporine-induced caspase-3/7 activity, which is rescued by dendrin depletion in YAP knockdown cells. Our findings elucidate YAP binding to dendrin as a prosurvival mechanism. The antiapoptotic signaling properties of YAP in podocytes could hold significance in the quest for targeted therapeutics aimed at preventing podocyte loss.

Highlights

Dendrin can relocate from the cytoplasm to the nucleus to promote podocyte apoptosis
We tested whether Yes-associated protein (YAP) can antagonize staurosporine-induced proapoptotic dendrin signaling in HEK293 cells co-transfected with GFP-dendrin and FLAG-YAP2, FLAG-YAP2⌬WW that cannot bind to dendrin (Fig. 1A), or FLAG-Raver serving as negative control
The results of this study revealed that YAP can bind to dendrin, thereby acting as inhibitor of proapoptotic nuclear dendrin signaling

Summary

Background

Dendrin can relocate from the cytoplasm to the nucleus to promote podocyte apoptosis. Cloning of the YAP gene and the characterization of its protein product helped to identify a modular protein domain, known as the WW domain, which mediates interaction with ligands containing PPXY motif (where X is any amino acid) [4, 5] Apart from its function in the cytoplasm, YAP is a transcriptional co-activator that interacts preferentially with the TEA domain family of transcription factors promoting expression of target genes important in cell survival, chemotaxis, differentiation, and proliferation [2, 6]. In response to glomerular injury, dendrin relocates to the podocyte nucleus, thereby promoting apoptosis [17, 20] As it stands, no signaling mechanisms have been identified that can antagonize dendrin-mediated cell death signaling. We show that YAP can bind to dendrin, thereby acting as an endogenous inhibitor of proapoptotic dendrin signaling in podocytes

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION