Carboxyl terminus of Plakophilin-1 recruits it to plasma membrane, whereas amino terminus recruits desmoplakin and promotes desmosome assembly |
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Authors: | Sobolik-Delmaire Tammy Katafiasz Dawn Wahl James K |
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Affiliation: | Department of Oral Biology, University of Nebraska Medical Center College of Dentistry and Nebraska Center for Cellular Signaling, Omaha, Nebraska 68138, USA. |
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Abstract: | Plakophilins are armadillo repeat-containing proteins, initially identified as desmosomal plaque proteins that have subsequently been shown to also localize to the nucleus. Loss of plakophilin-1 is the underlying cause of ectodermal dysplasia/skin fragility syndrome, and skin from these patients exhibits desmosomes that are reduced in size and number. Thus, it has been suggested that plakophilin-1 plays an important role in desmosome stability and/or assembly. In this study, we used a cell culture system (A431DE cells) that expresses all of the proteins necessary to assemble a desmosome, except plakophilin-1. Using this cell line, we sought to determine the role of plakophilin-1 in de novo desmosome assembly. When exogenous plakophilin-1 was expressed in these cells, desmosomes were assembled, as assessed by electron microscopy and immunofluorescence localization of desmoplakin, into punctate structures. Deletion mutagenesis experiments revealed that amino acids 686-726 in the carboxyl terminus of plakophilin-1 are required for its localization to the plasma membrane. In addition, we showed that amino acids 1-34 in the amino terminus were necessary for subsequent recruitment of desmoplakin to the membrane and desmosome assembly. |
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