|
|
 Previous Article | Table of Contents | Next Article 
The Exon 46-Encoded Sequence Is Essential for Stability of Human Erythroid  -Spectrin and Heterodimer Formation
Rick Wilmotte,
Sandra L. Harper,
Jeanine A. Ursitti,
Joëlle Maréchal,
Jean Delaunay, and
David W. Speicher
From the Laboratoire de Génétique Moléculaire Humaine, CNRS URA 1171, Institut Pasteur de Lyon, Lyon, France; and The Wistar Institute, Philadelphia, PA.
Human erythroid  -spectrin alleles responsible for hereditary elliptocytosis (HE alleles) undergo increased incorporation into red blood cell membranes when the polymorphism LELY (LELY: Low Expression LYon) occurs in trans. The LELY polymorphism is characterized by a mutation in exon 40 at codon 1857 (CTA  GTA, Leu Val) and the partial (50%) skipping of exon 46, which encodes residues 2177-2182 (Wilmotte et al, J Clin Invest 91:2091, 1993). Both of these peptide sequence alterations are located within the region of the -chain involved in initiating heterodimer assembly, and either or both mutations could potentially contribute to decreased incorporation of -chains from the LELY allele in heterozygotes into red blood cell membranes. These possibilities were evaluated by testing the protease resistance and in vitro binding properties of normal and mutant recombinant 4-motif subunit peptides containing the dimer initiation region. The two forms of spectrin produced by alternative mRNA splicing of the LELY allele were represented by 18-211857, a peptide with the codon 1857 mutation and retaining the exon 46 encoded sequence, and 18-211857- 46, a peptide carrying both the 1857 codon mutation and the exon 46 deletion. The properties of these two recombinant peptides were compared with 18-21, a peptide with the normal sequence at codon 1857 and retaining the exon 46 encoded sequence. The codon 1857 mutation does not adversely affect dimer formation, but it is responsible for the increased trypsin cleavage between the IV and V domains that was the characteristic feature initially used to identify the LELY (SpV/41) polymorphism (Alloisio et al, J Clin Invest 87:2169, 1991). Deletion of the six amino acids encoded by exon 46 perturbs folding of the 21 motif, because this region of the 18-211857-46 peptide is rapidly degraded and this recombinant peptide is unusually prone to self-aggregation. Exon 46 deletion reduces, but does not eliminate, dimerization. Comparison of mild trypsin proteolytic products from an LELY homozygote and the two LELY recombinant peptides strongly suggests that little, if any, of the 50% of the chains from the LELY allele that contain the exon 46 deletion are incorporated into the mature erythroid membrane. Based on the in vitro analysis of recombinant LELY peptides, the inability of detectable amounts of exon 46- chains to assemble into the mature membrane skeleton in vivo is probably due to a combination of decreased dimer binding affinity and increased proteolytic degradation of these mutant chains.
Blood, Vol. 90 No. 10 (November 15), 1997:
pp. 4188-4196
© 1997 by The American Society of Hematology.
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
D. Li, H.-Y. Tang, and D. W. Speicher
A Structural Model of the Erythrocyte Spectrin Heterodimer Initiation Site Determined Using Homology Modeling and Chemical Cross-linking
J. Biol. Chem.,
January 18, 2008;
283(3):
1553 - 1562.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. P. Johnson, M. Gaetani, V. Ortiz, N. Bhasin, S. Harper, P. G. Gallagher, D. W. Speicher, and D. E. Discher
Pathogenic proline mutation in the linker between spectrin repeats: disease caused by spectrin unfolding
Blood,
April 15, 2007;
109(8):
3538 - 3543.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. M. Ginolhac, S. Gad, M. Corbex, B. Bressac-de-Paillerets, A. Chompret, Y.-J. Bignon, J.-P. Peyrat, J. Fournier, C. Lasset, S. Giraud, et al.
BRCA1 Wild-Type Allele Modifies Risk of Ovarian Cancer in Carriers of BRCA1 Germ-Line Mutations
Cancer Epidemiol. Biomarkers Prev.,
February 1, 2003;
12(2):
90 - 95.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
