A single amino acid substitution flanking the fourth calcium binding domain of alpha IIb prevents maturation of the alpha IIb beta 3 integrin complex. J Biol Chem 1994 Feb 11;269(6):4450-7
Date
02/11/1994Pubmed ID
7508443Scopus ID
2-s2.0-0028071221 (requires institutional sign-in at Scopus site) 83 CitationsAbstract
To define specific structural domains involved in the biosynthesis and processing of integrin subunits, we examined the biosynthesis of normal and mutated forms of the platelet-specific integrin alpha IIb beta 3. Platelet mRNA was isolated from a Glanzmann thrombasthenic patient who failed to express significant levels of the glycoprotein (GP) IIb-IIIa complex on the platelet surface. Sequence analysis of polymerase chain reaction-amplified platelet GPIIb mRNA revealed a Gly418-->Asp amino acid substitution in GPIIb. Gly418 is a highly conserved residue that flanks the fourth calcium binding domain of GPIIb. Cotransfection of Asp418 GPIIb and GPIIIa plasmid constructs into COS-7 cells resulted in the accumulation of a pre-GPIIb-IIIa complex that failed to reach the cell surface, in effect recreating the thrombasthenic phenotype. Pulse-chase and endoglycosidase studies demonstrated that the biosynthetic blockade occurred in a pre-Golgi compartment. Removal of the negatively charged carboxyl group of Asp418 GPIIb, creating Ala418 GPIIb, rescued intracellular transport and surface expression of the integrin complex. Mutagenesis of a homologous Gly within the integrin alpha subunit alpha v also resulted in the failure to express alpha v beta 3 on the cell surface. These results suggest that the presence of a small, uncharged amino acid 6-8 residues amino-terminal to the calcium coordination complex is crucial for the proper folding and maturation of integrin complexes.
Author List
Wilcox DA, Wautier JL, Pidard D, Newman PJAuthor
David A. Wilcox PhD Professor in the Pediatrics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceBase Sequence
Binding Sites
Biological Transport
Calcium
Cell Membrane
DNA Primers
Gene Expression
Glycine
Golgi Apparatus
Humans
Integrins
Molecular Sequence Data
Mutagenesis, Site-Directed
Platelet Glycoprotein GPIIb-IIIa Complex
Platelet Membrane Glycoproteins
Protein Processing, Post-Translational
RNA, Messenger
Sequence Alignment
Sequence Homology, Amino Acid
Solubility
Structure-Activity Relationship
Thrombasthenia
Transfection