Folliculin interacts with p0071 (plakophilin-4) and deficiency is associated with disordered RhoA signalling, epithelial polarization and cytokinesis

Michael S Nahorski,Xiaohong Lu,Eamonn R Maher,Mechthild Hatzfeld,Laurence Seabra,Jeff A Klomp,Paul Gissen,Ania Straatman-Iwanowska,Bin T Teh,Anne Reiman,Aileen Wingenfeld

doi:10.1093/hmg/dds378

Abstract

Inherited mutations in the folliculin (FLCN) gene cause the Birt-Hogg-Dubé syndrome of familial hair follicle tumours (fibrofolliculomas), lung cysts and kidney tumours. Though folliculin has features of a tumour suppressor, the precise function of the FLCN gene product is not well characterized. We identified plakophilin-4 (p0071) as a potential novel folliculin interacting protein by yeast two-hybrid analysis. We confirmed the interaction of folliculin with p0071 by co-immunoprecipitation studies and, in view of previous studies linking p0071 to the regulation of rho-signalling, cytokinesis and intercellular junction formation, we investigated the effect of cell folliculin status on p0071-related functions. Folliculin and p0071 partially co-localized at cell junctions and in mitotic cells, at the midbody during cytokinesis. Previously, p0071 has been reported to regulate RhoA signalling during cytokinesis and we found that folliculin deficiency was associated with increased expression and activity of RhoA and evidence of disordered cytokinesis. Treatment of folliculin-deficient cells with a downstream inhibitor of RhoA signalling (the ROCK inhibitor Y-27632) reversed the increased cell migration phenotype observed in folliculin-deficient cells. Deficiency of folliculin and of p0071 resulted in tight junction defects and mislocalization of E-cadherin in mouse inner medullary collecting duct-3 renal tubular cells. These findings suggest that aspects of folliculin tumour suppressor function are linked to interaction with p0071 and the regulation of RhoA signalling.

Highlights

Germline mutations in the folliculin (FLCN) gene cause Birt Hogg Dube (BHD) syndrome, an inherited cancer predisposition disorder, characterized by benign tumours of the hair follicles on the face and upper torso, renal cell carcinoma (RCC) and lung cysts and pneumothorax [1,2]
To further elucidate the mechanisms of folliculin tumour suppression, we undertook a yeast two-hybrid screen and identified PKP4 (p0071) as a potential folliculin interacting protein. p0071 is a member of the armadillo superfamily and is part of a subtype of armadillo proteins of which p120ctn is the prototype. p120ctn proteins include p0071, d-catenin, ARCF and the more distantly related PKP1 – 3
The characteristic armadillo-repeat domain shared by p120 family proteins is crucial in the interaction of p120 proteins with classical type I and II cadherins, resulting in the stabilization of cadherins at membrane adherens junctions [23]. p0071

Summary

Introduction

Germline mutations in the folliculin (FLCN) gene cause Birt Hogg Dube (BHD) syndrome, an inherited cancer predisposition disorder, characterized by benign tumours of the hair follicles (fibrofolliculomas) on the face and upper torso, renal cell carcinoma (RCC) and lung cysts and pneumothorax [1,2]. The FLCN gene, mapped to chromosome 17p11.2, is a tumour suppressor gene and biallelic FLCN inactivation has been described in RCC from patients with BHD syndrome [6,7]. Germline FLCN mutations have been described in patients with inherited RCC and familial spontaneous pneumothorax [8,9].

Methods

Results

Conclusion