Chapter 63 Collagens, Elastic Fibers, and Other Extracellular Matrix Proteins of the Dermis Flashcards
most of collagens have a modular structure, and composed of one, a few, or several copies of a limited set of individual structural modules, also called
domains
____ determines the biophysical properties of connective tissues
ECM
collagens approx ___% of the dry weight of the dermis
80%
Classical and 1st recognized physiologic role of collagens in the skin _________
provide tensile properties
first member of the collagens family, the most abundant collagens in the dermis and most other connective tissues
Type I collagen
______ the smallest amino acid, accounts for approximately 1/3 the total number of amino acids, evenly distributed along the polypeptide
glycine (Gly)
______ in every 3rd position are necessary for the triple-helical conformation of the collagens molecule, and ______ plays a critical role in stabilizing the triple helix at body temperature
glycine
hydroxyproline
Triple-helical conformation defines the so-called ______, and it gives type I collagens many of its unique properties
collagenous domain
_____ collagens represents approx 10% of the total collagens in the adult human dermis
Type III collagen
relatively high content of hydroxyproline and glycine and the presence of one cysteine residue
______ and _____form the relatively broad extracellular fibers that are primarily responsible for the tensile strength of the human dermis
collagen types I and III
_____ represents < 5% of the total collagens
Type V collagen
postulated to regulate the fiber diameter during fibrillogenesis
mutations in type V collagens genes in patients with classical autosomal dominant forms (types I and II) of Ehlers–Danlos syndrome
absence of _____ autosomal recessive form of Ehlers-Danlos syndrome
Tenascin X expression
_____ typical component of basement membranes, where it forms a lattice rather than the fibers characteristic of dermal collagens
collagen type IV
contain imperfect Gly-X-Y triplets, a feature that confers flexibility to the triple-helical domain of the molecule
A noncollagenous globular domain at the amino-terminal part of the molecule mediates dimer formation, while a short segment at the carboxyl-terminal region of the molecule allows for tetramer assembly, altogether resulting in the so-called “chicken-wire” assembly network for collagens type IV
mutation in _____ gene has been identified in a family with autosomal dominant porencephaly and infantile hemiparesis
mutation in the COL4A1 gene
mutations in the COL4A5 gene result in _____, an X-linked renal disease
Alport syndrome
Autoantibodies recognizing the collagens α3(IV) chain underlie ______
Goodpasture syndrome
______ collagen forms specific microfibrils in the dermis
Type VI collagens
_____ collagens forms the anchoring fibrils of the DEJ
type VII collagens
Mutations in each of the three type VI collagens genes can lead to different forms of _______
congenital muscular dystrophy
Alterations in the expression, structure, or molecular interactions of ____ with other basement membrane components could result in dystrophic epidermolysis bullosa (DEB)
type VII collagen
COL7A1
_____ collagen, Transmembrane protein anchored in the membrane of basal keratinocytes, with an intracellular domain and a large extracellular domain, or ectodomain, which is a component of the basement membrane at DEJ
type XVII collagen
initially identified as the 180-kDa bullous pemphigoid antigen (BPAG2), which was recognized by circulating autoantibodies in the sera of patients with bullous pemphigoid or herpes gestationis
mutations in the corresponding gene _____ that underlie a nonlethal variant of junctional epidermolysis bullosa, generalized atrophic benign epidermolysis bullosa
gene COL17A1
Collagens genes, like most eukaryotic genes, are large, multiexon genes interrupted at several points by noncoding DNA sequences called _____
introns
Precursor polypeptides of procollagen, so-called ______, are synthesized on the ribosomes of the rough endoplasmic reticulum in fibroblasts and related cells
pre-proa chains