A role for plakophilin-1 in the initiation of desmosome assembly.
Plakophilins (pkp-1, -2, and -3) comprise a family of armadillo-repeat containing proteins that are found in the desmosomal plaque and in the nucleus. Plakophilin-1 is most highly expressed in the suprabasal layers of the epidermis and loss of plakophilin-1 expression results in skin fragility-ectodermal dysplasia syndrome, which is characterized by a reduction in the number and size of desmosomes in the epithelia of affected individuals. To investigate the role of plakophilin-1 during desmosome formation, we fused plakophilin-1 to the hormone-binding domain of the estrogen receptor to create a fusion protein (plakophilin-1/ER) that can be activated in cell culture by the addition of 4-hydroxytamoxifen. When plakophilin-1/ER was expressed in A431 cells it was incorporated into endogenous desmosomes and did not disrupt desmosome formation. A derivative of A431 cells (A431D) do not form desmosomes, even though they express all the components believed to be necessary for desmosome assembly. Expression and activation of plakophilin-1/ER in A431D cells resulted in punctate desmoplakin staining on the cell surface. Co-expression of a classical cadherin (N-cadherin) and plakophilin-1/ER in A431D cells resulted in punctate desmoplakin staining at cell-cell borders. These data suggest that plakophilin-1 can induce assembly of desmosomal components in A431D cells in the absence of a classical cadherin; however a classical cadherin (N-cadherin) is required to direct assembly of desmosomes between adjacent cells. The activatable plakophilin-1/ER system provides a unique culture system to study the assembly of the desmosomal plaque in culture.
Wahl
James K
JK
University of Nebraska Medical Center, College of Dentistry, Department of Oral Biology and Nebraska Center for Cellular Signaling, Omaha, Nebraska 68198, USA. jwahl@unmc.edu
D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003896:Desmosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008854:Microscopy, Electron; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors
D013629:Tamoxifen; C016601:afimoxifene