Regulation of desmosomal hyperadhesion in epidermal barrier function and tissue integrity

• Applicant: Professorin Dr. Mechthild Hatzfeld
• Subject Area: Cell Biology ; Dermatology
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 326600997

• Final Report Year: 2021

Final Report Abstract

We have identified a previously unknown function of the Pkcδ isoform in the regulation of desmosome dynamics and stability. As a major target we identified Pkp3 which becomes redistributed from tricellular contacts to lateral membranes upon Pkc activation. A broad spectrum Pkc inhibitor as well as Pkcδ knockdown prevented this re-distribution whereas Pkcα knockdown had no such effect. Pkc activation had no effect on phosphorylation or localization of a Pkp3-S313/314A mutant whereas the phospho-mimicry mutant copied the effects of Pkc-modified wtPkp3. Since Pkp3 is highly dynamic we conclude that Pkcδ mediated phosphorylation is an important regulator of desmosome dynamics. Pkps are also modified by palmitoylation. A broad spectrum palmitoylation inhibitor interfered with desmosome formation but had a milder effect on desmosome maturation whereas inhibition of depalmitoylating enzymes had the opposite effects. Both treatments reduced intercellular cohesion. Together with the finding that only ~ 50% of Pkps were palmitoylated this suggests a dynamic equilibrium between palmitoylation and depalmitoylation. The palmitoyltransferase Zdhhc5 is essential for intercellular cohesion and Pkp1 and Pkp3 acylation is lost upon Zdhhc5 knockdown. Pkps associate with Zdhhc5 at the plasma membrane suggesting that they become palmitoylated at the desmosome. However, an association with Zdhhc7 at the Golgi was also observed. Thus distinct palmitoyltransferases might be involved in the regulation of desmosomal proteins affecting their transport, incorporation into and maturation of desmosomes. Unraveling this complex interplay of palmitoylation and depalmitoylation in detail and its interaction with kinase-mediated phosphorylation requires further investigation.

Publications

• Desmosomes and Intermediate Filaments: Their Consequences for Tissue Mechanics. Cold Spring Harb Perspect Biol. 2017 Jun 1;9(6):a029157
  Keil R, Magin TM
  
• 14-3-3 proteins regulate desmosomal adhesion via plakophilins. J Cell Sci. 2018 May 22;131(10):jcs212191
  Rietscher K, Keil R, Jordan A, Hatzfeld M
  
• Cross-Talk between Hemidesmosomes and Focal Adhesions: A Primer for Wound Healing, Blistering Skin Disease, and Skin Aging. J Invest Dermatol. 2019 Sep;139(9):1854-1856
  Hatzfeld M, Magin TM
  
• Plakophilin 1 but not plakophilin 3 regulates desmoglein clustering. Cell Mol Life Sci. 2019 Sep;76(17):3465-3476
  Plakophilin 1 but not plakophilin 3 regulates desmoglein clustering. Fuchs M, Foresti M, Radeva MY, Kugelmann D, Keil R, Hatzfeld M, Spindler V, Waschke J, Vielmuth F
  
• Plakophilin 3 phosphorylation by ribosomal S6 kinases supports desmosome assembly. J Cell Sci. 2020 Apr 16;133(8): jcs238295
  Müller L, Rietscher K, Keil R, Neuholz M, Hatzfeld M