Changes in cell-cell adhesion and remodeling of cellular junctions are an important prerequisite for cell migration. Desmosomes are prominent cadherin based cell-cell adhesive junctions found in epithelial tissues such as the skin and oral mucosa. These junctions associate with the keratin intermediate filament cytoskeleton and provide a means to link the cytoskeletal systems between adjacent cells in an epithelial tissue. Therefore, desmosomes provide epithelial tissues with a means to withstand mechanical stress. During normal physiologic processes such as epidermal development and wound healing, epithelial cells must remodel their adhesive contacts to allow cells to migrate in a controlled manner. In addition, tumor cells remodel their adhesive contacts with their neighbors and often acquire the ability to detach from the primary tumor and invade the underlying stroma. The mechanisms that coordinate the re-modeling of adhesive junctions and promote a migratory phenotype are largely unknown. The focus of this project is to elucidate the role of palmitoylation in the regulation of desmosome dynamics and in turn epithelial cell migration and adhesion. We have recently discovered that desmosomal cadherins and select desmosomal plaque proteins are palmitoylated and disruption of palmitoylation has profound effects on desmosome assembly and desmosomal adhesiveness. Specifically, disruption of plakophilin palmitoylation results in perturbed desmosomal adhesion in a dominant negative manner. Based on these findings we propose that palmitoylation of desmosomal components plays an important regulatory role in desmosome dynamics. We will test our hypothesis by first determining the mechanisms regulating plakophilin-3 palmitoylation and determine the effect of disrupted palmitoylation on desmosome assembly and cell migration. Secondly, we will identify the enzymes responsible for palmitoylation/depalmitoylation of plakophilin-3 and determine their role in desmosome dynamics. This R15 project will be the first to investigate palmitoylation as a novel mechanism of regulation for desmosomal adhesion and will provide the basis for the investigation of palmitoylation as a potential therapeutic target to control cell migration of keratinocytes during normal wound healing processes or tumor cells during metastasis.
The mechanisms controlling cell-cell adhesion are poorly understood. We have identified palmitoylation as a novel post-translational modification that regulates the assembly of desmosomes and affects epithelial cell-cell adhesion. Elucidation of the mechanisms controlling palmitoylation dynamics of desmosomal components will allow a better understanding of the events underlying cell adhesion and epithelial cell migration.
