The amino-terminal domain of desmoplakin binds to plakoglobin and clusters desmosomal cadherin-plakoglobin complexes.
The desmosome is a highly organized plasma membrane domain that couples intermediate filaments to the plasma membrane at regions of cell-cell adhesion. Desmosomes contain two classes of cadherins, desmogleins, and desmocollins, that bind to the cytoplasmic protein plakoglobin. Desmoplakin is a desmosomal component that plays a critical role in linking intermediate filament networks to the desmosomal plaque, and the amino-terminal domain of desmoplakin targets desmoplakin to the desmosome. However, the desmosomal protein(s) that bind the amino-terminal domain of desmoplakin have not been identified. To determine if the desmosomal cadherins and plakoglobin interact with the amino-terminal domain of desmoplakin, these proteins were co-expressed in L-cell fibroblasts, cells that do not normally express desmosomal components. When expressed in L-cells, the desmosomal cadherins and plakoglobin exhibited a diffuse distribution. However, in the presence of an amino-terminal desmoplakin polypeptide (DP-NTP), the desmosomal cadherins and plakoglobin were observed in punctate clusters that also contained DP-NTP. In addition, plakoglobin and DP-NTP were recruited to cell-cell interfaces in L-cells co-expressing a chimeric cadherin with the E-cadherin extracellular domain and the desmoglein-1 cytoplasmic domain, and these cells formed structures that were ultrastructurally similar to the outer plaque of the desmosome. In transient expression experiments in COS cells, the recruitment of DP-NTP to cell borders by the chimera required co-expression of plakoglobin. Plakoglobin and DP-NTP co-immunoprecipitated when extracted from L-cells, and yeast two hybrid analysis indicated that DP-NTP binds directly to plakoglobin but not Dsg1. These results identify a role for desmoplakin in organizing the desmosomal cadherin-plakoglobin complex and provide new insights into the hierarchy of protein interactions that occur in the desmosomal plaque.
Kowalczyk
A P
AP
Department of Dermatology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Bornslaeger
E A
EA
Borgwardt
J E
JE
Palka
H L
HL
Dhaliwal
A S
AS
Corcoran
C M
CM
Denning
M F
MF
Green
K J
KJ
D000818:Animals; D015820:Cadherins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D051187:Desmocollins; D051183:Desmoglein 1; D051182:Desmogleins; D051180:Desmoplakins; D003896:Desmosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005110:Extracellular Space / Q000737:chemistry / Q000235:genetics; D006801:Humans; D007739:L Cells; D046911:Macromolecular Substances; D051379:Mice; D010455:Peptides / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D051178:alpha Catenin; D051185:gamma Catenin
C495273:CTNNA1 protein, human; D015820:Cadherins; C495272:Ctnna1 protein, mouse; D003598:Cytoskeletal Proteins; C495297:DSG1 protein, human; C495294:DSP protein, human; D051187:Desmocollins; D051183:Desmoglein 1; D051182:Desmogleins; D051180:Desmoplakins; C495299:Dsg1a protein, mouse; C495295:Dsp protein, mouse; D046911:Macromolecular Substances; D010455:Peptides; D011993:Recombinant Fusion Proteins; D051178:alpha Catenin; D051185:gamma Catenin