Proteoglycan biosynthesis by human corneas from patients with types 1 and 2 macular corneal dystrophy.
Corneal buttons were obtained from patients with types 1 and 2 macular corneal dystrophy (MCD) and from control patients with Fuchs' dystrophy or keratoconus. Buttons were incubated for 20 h in the presence of [3H]glucosamine or [2-3H]mannose. Radiolabeled proteoglycans and lactosaminoglycan-glycoproteins (L-GPs) were purified using chromatography on Q-Sepharose, Superose 6, and octyl-Sepharose. They were identified using chondroitinase ABC, keratanase or endo-beta-galactosidase digestion, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis or Superose 6 chromatography. This study confirms previous reports that type 1 MCD corneas synthesize a normal dermatan sulfate-proteoglycan (DS-PG) and an abnormal keratan sulfate-proteoglycan (KS-PG). The data indicate that typ 1 MCD corneas synthesize L-GP instead of KS-PG. This L-GP has a core protein of similar hydrophobicity (elution from octyl-Sepharose) and nearly similar mass (42 kDa) as the core protein of the KS-PG. It has identical glycoconjugates as those of the KS-PG except that they lack sulfate. Thus, type 1 MCD fails to synthesize keratan sulfate as a result of a defect in a sulfotransferase specific for sulfating lactosaminoglycans. Further, proteoglycans synthesized by a cornea from a patient with type 2 MCD were studied. This cornea synthesized a normal ratio of KS-PG to DS-PG although net synthesis of proteoglycans was approximately 30% below normal. The KS-PG appeared normal whereas the DS-PG had dermatan sulfate chains that were approximately 40% shorter than normal.
Midura
R J
RJ
Proteoglycan Chemistry Section, Bone Research Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
Hascall
V C
VC
MacCallum
D K
DK
Meyer
R F
RF
Thonar
E J
EJ
Hassell
J R
JR
Smith
C F
CF
Klintworth
G K
GK
D002478:Cells, Cultured; D002852:Chromatography, Ion Exchange; D003315:Cornea / Q000378:metabolism*; D003317:Corneal Dystrophies, Hereditary / Q000378:metabolism*; D005944:Glucosamine / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis / Q000302:isolation & purification; D006801:Humans; D007640:Keratoconus / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D008970:Molecular Weight; D011509:Proteoglycans / Q000096:biosynthesis* / Q000302:isolation & purification; D012016:Reference Values; D014316:Tritium
D006023:Glycoproteins; D011509:Proteoglycans; D014316:Tritium; D005944:Glucosamine; D008358:Mannose