Biomaterial Database

Defining the interactions between intermediate filaments and desmosomes. 1998

E A Smith, and E Fuchs

Howard Hughes Medical Institute, The University of Chicago, Chicago, Illinois 60637, USA.

Desmoplakin (DP), plakoglobin (PG), and plakophilin 1 (PP1) are desmosomal components lacking a transmembrane domain, thus making them candidate linker proteins for connecting intermediate filaments and desmosomes. Using deletion and site-directed mutagenesis, we show that remarkably, removal of approximately 1% of DP's sequence obliterates its ability to associate with desmosomes. Conversely, when linked to a foreign protein, as few as 86 NH2-terminal DP residues are sufficient to target to desmosomes efficiently. In in vitro overlay assays, the DP head specifically associates with itself and with desmocollin 1a (Dsc1a). In similar overlay assays, PP1 binds to DP and Dsc1a, and to a lesser extent, desmoglein 1 (Dsg1), while PG binds to Dsg1 and more weakly to Dsc1a and DP. Interestingly, like DP, PG and PP1 associate with epidermal keratins, although PG is considerably weaker in its ability to do so. As judged by overlay assays, the amino terminal head domain of type II keratins appears to have a special importance in establishing these connections. Taken together, our findings provide new insights into the complexities of the links between desmosomes and intermediate filaments (IFs). Our results suggest a model whereby at desmosome sites within dividing epidermal cells, DP and PG anchor to desmosomal cadherins and to each other, forming an ordered array of nontransmembrane proteins that then bind to keratin IFs. As epidermal cells differentiate, PP1 is added as a molecular reinforcement to the plaque, enhancing anchorage to IFs and accounting at least partially for the increase in numbers and stability of desmosomes in suprabasal cells.

UI	MeSH Term	Description	Entries
D007382	Intermediate Filaments	Cytoplasmic filaments intermediate in diameter (about 10 nanometers) between the microfilaments and the microtubules. They may be composed of any of a number of different proteins and form a ring around the cell nucleus.	Tonofilaments,Neurofilaments,Filament, Intermediate,Filaments, Intermediate,Intermediate Filament,Neurofilament,Tonofilament
D007633	Keratins	A class of fibrous proteins or scleroproteins that represents the principal constituent of EPIDERMIS; HAIR; NAILS; horny tissues, and the organic matrix of tooth ENAMEL. Two major conformational groups have been characterized, alpha-keratin, whose peptide backbone forms a coiled-coil alpha helical structure consisting of TYPE I KERATIN and a TYPE II KERATIN, and beta-keratin, whose backbone forms a zigzag or pleated sheet structure. alpha-Keratins have been classified into at least 20 subtypes. In addition multiple isoforms of subtypes have been found which may be due to GENE DUPLICATION.	Cytokeratin,Keratin Associated Protein,Keratin,Keratin-Associated Proteins,alpha-Keratin,Associated Protein, Keratin,Keratin Associated Proteins,Protein, Keratin Associated,alpha Keratin
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D011506	Proteins	Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.	Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D003598	Cytoskeletal Proteins	Major constituent of the cytoskeleton found in the cytoplasm of eukaryotic cells. They form a flexible framework for the cell, provide attachment points for organelles and formed bodies, and make communication between parts of the cell possible.	Proteins, Cytoskeletal
D003896	Desmosomes	A type of junction that attaches one cell to its neighbor. One of a number of differentiated regions which occur, for example, where the cytoplasmic membranes of adjacent epithelial cells are closely apposed. It consists of a circular region of each membrane together with associated intracellular microfilaments and an intercellular material which may include, for example, mucopolysaccharides. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990; Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Desmosome
D004817	Epidermis	The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein