Plakophilin-3, a novel armadillo-like protein present in nuclei and desmosomes of epithelial cells.
We report on a novel Armadillo-like protein, termed plakophilin-3. The human protein, which is encoded by a 2.8 kb messenger RNA, has a predicted molecular mass of 87 kDa. The protein comprises 10 Armadillo-like repeats, preceded by an amino-terminal region of 293 amino acid residues and followed by a short carboxy-terminal region of 27 amino acid residues. Plakophilin-3 is classified as a member of the p120(ctn)/plakophilin subfamily of Armadillo proteins based on the number and organization of the Armadillo repeats and its high sequence similarity to other members of this family. CLUSTAL W alignment of p120(ctn)/plakophilin subfamily members showed the plakophilin-3 protein to be most similar to plakophilin-1 and -2. Western blot analysis of plakophilin-3 revealed expression in all epithelial cell lines tested but not in foreskin fibroblasts and various sarcoma-derived cell lines. This is unlike most other members of the p120(ctn)/plakophilin subfamily, which are widely expressed. By immunofluorescence, the plakophilin-3 protein was colocalized with desmoglein in desmosomes of epithelial cells. In addition, an intriguing speckle-like nuclear staining was observed. Hence, like plakophilin-1 and -2, plakophilin-3 displays a dual intracellular location, i.e. in the desmosomal plaque and in the nucleus. These results suggest the involvement of plakophilin-3 in both desmosome-dependent adhesion and signaling pathways. Furthermore, the human plakophilin-3 gene was mapped on the chromosomal locus 11p15 by fluorescent in situ hybridization.
Bonné
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Molecular Cell Biology Unit, Department of Molecular Biology, Flanders Interuniversity Institute for Biotechnology (VIB) - University of Gent, Ledeganckstraat 35, B-9000 Gent, Belgium.
van Hengel
J
J
Nollet
F
F
Kools
P
P
van Roy
F
F
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002874:Chromosome Mapping; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D003896:Desmosomes / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D051191:Plakophilins; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid
D015815:Cell Adhesion Molecules; D017931:DNA Primers; C495335:PKP1 protein, human; C495339:PKP3 protein, human; C495336:Pkp1 protein, mouse; C495340:Pkp3 protein, mouse; D051191:Plakophilins; D011506:Proteins; D012333:RNA, Messenger