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Keratinocyte secretion of cyclophilin B via the constitutive pathway is regulated through its cyclosporin-binding site

Lookup NU author(s): Dr Paula Fearon, Carole Todd, Dr Aparna Sinha, Professor Nick ReynoldsORCiD


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Cyclophilin B (CypB) is an endoplasmic reticulum (ER)-resident member of the cyclophilin family of proteins that bind cyclosporin A (CsA). We report that as in other cell types, CypB trafficked from the ER and was secreted by keratinocytes into the media in response to CsA. Concentrations as low as 1 pM of CsA induced secretion of CypB. Using brefeldin A, we showed that CypB is secreted from keratinocytes via the constitutive secretory pathway. We defined that substitution of tryptophan residue 128 in the CsA-binding site of CypB with alanine resulted in dissociation of CypBW128A-green fluorescent protein (GFP) from the ER. Photobleaching studies revealed a significant reduction in the diffusible mobility of CypBW128A-GFP compared with CypBWT-GFP, consistent with redistribution of CypBW128A-GFP into secretory vesicles disconnected from the ER/Golgi network. Furthermore, CsA significantly decreased the mobility of CypBWT-GFP but not CypBW128A-GFP. These studies demonstrate that therapeutically relevant concentrations of CsA regulate secretion of CypB by keratinocytes, and that a key residue within the CsA-binding site of CypB controls retention of CypB within the ER and regulates entry into the secretory pathway. As keratinocytes express CypB receptors (CD147) and CypB exhibits chemotactic properties, these data have implications for the therapeutic effects of CsA in inflammatory skin disease.

Publication metadata

Author(s): Fearon P, Lonsdale-Eccles AA, Ross OK, Todd C, Sinha A, Allain F, Reynolds NJ

Publication type: Article

Publication status: Published

Journal: Journal of Investigative Dermatology

Year: 2011

Volume: 131

Issue: 5

Pages: 1085-1094

Print publication date: 27/01/2011

ISSN (print): 0022-202X

ISSN (electronic): 1523-1747

Publisher: Nature Publishing Group


DOI: 10.1038/jid.2010.415


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