Kindlins and Rho GTPase-mediated signaling pathways
Final Report Abstract
Kindlins are a family of integrin adapter and cell-matrix adhesion proteins which are causally linked to human genetic disorders. Kindlin-1 and -2 are expressed in the skin. Kindlin-2 is a ubiquitously expressed protein with manifold functions and interactions. We uncovered the overlapping roles of kindlin-1 and kindlin-2 in maintaining epithelial integrity and showed that the phenotype of kindlin-1 deficient cells can be modulated by regulating kindlin-2 gene expression, and vice versa. The contribution of kindlin-2 to integrin based cell-matrix adhesions has been extensively explored, while other integrin-independent roles emerge. Because of the early involvement of kindlin-2 in development, no viable animal models with its constitutional knockout are available to study its physiological functions in adult skin. We uncovered a critical physiological role of kindlin-2 in the epidermis by using a skin equivalent model with shRNA mediated knock-down of kindlin-2 in keratinocytes. Kindlin-2 deficient keratinocytes built stratified epidermal layers, but displayed impaired dermal-epidermal and intraepidermal adhesion, and barrier function. Co-immunoprecipitation studies revealed the underlying mechanisms and demonstrated that kindlin-2 interacts with both integrin and cadherin based adhesions. Subsequently, in kindlin-2 deficient keratinocytes, reduced cellcell adhesion was associated with abnormal cytoplasmic distribution of adherens junction and desmosomal proteins, which was dependent on RhoA activation. Direct activation of RhoA using the recombinant bacterial cytotoxic necrotizing factor y reverted the abnormal phenotype and barrier function of kindlin-2 deficient keratinocytes and skin equivalents. These findings have physiologic and pathologic significance since kindlin-2 expression modulates the phenotype in Kindler syndrome, a skin fragility disorder caused by kindlin-1 deficiency. Our results suggest that pharmacologic regulation of RhoGTPase activity may represent a therapeutic option for skin fragility.
Publications
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Kindlin-1 and -2 have overlapping functions in epithelial cells implications for phenotype modification. Am J Pathol. 2011 Mar;178(3):975-82
He Y, Esser P, Heinemann A, Bruckner-Tuderman L, Has C
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European Toxicology meeting (Etox 16) 22.06.-26.06. 2013, Freiburg: Rescue of Kindlin deficiency using bacterial toxins
Tanja Sonnenwald, Yinghong He, Cristina Has und Gudula Schmidt
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Gordon Research Conference on Collagens, 18.07.2013, New London: Focal adhesions and skin fragility disorders
Has C
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International Investigative Dermatology, 8-11.05.2013, Edinburgh: Role of kindlin-2 in epidermal homeostasis
He Y, Sonnenwald T, Hansen U, Sprenger A, Fritsch A, Schmidt G, Bruckner-Tuderman L, Has C
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Symposium „Signaling and Sorting“ 10.04.-12.04. 2013, Freiburg: Rescue of Kindlin deficiency using bacterial toxins
Tanja Sonnenwald, Yinghong He, Cristina Has und Gudula Schmidt
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(2014). RhoA activation by CNFy restores cell-cell adhesion in kindlin-2 deficient keratinocytes. J Pathol
He, Y., Sonnenwald, T., Sprenger, A., Hansen, U., Dengjel, J., Bruckner-Tuderman, L., Schmidt, G. and Has, C.
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The missense mutation p.R1303Q in type XVII collagen underlies junctional epidermolysis bullosa resembling Kindler syndrome. J Invest Dermatol. 2014 Mar;134(3):845-9
Has C, Kiritsi D, Mellerio JE, Franzke CW, Wedgeworth E, Tantcheva-Poor I, Kernland-Lang K, Itin P, Simpson MA, Dopping-Hepenstal PJ, Fujimoto W, McGrath JA, Bruckner-Tuderman L
