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GPIIb and GPIIIa amino acid sequences deduced from human megakaryocyte cDNAs

P Frachet1, G Uzan, D Thevenon

  • 1DRF/Laboratoire d'Hématologie, Inserm U217, Grenoble, France.

Molecular Biology Reports
|February 1, 1990
PubMed

Insights

This study identified full-length cDNAs for platelet GPIIb and GPIIIa proteins in megakaryocytes. Nucleotide differences were found compared to HEL cells, revealing important variations in platelet glycoprotein synthesis.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Hematology

Background:

  • Platelet glycoprotein (GP) IIbIIIa is crucial for platelet aggregation.
  • Its synthesis is primarily restricted to megakaryocytes and megakaryocytic cell lines.
  • Previous studies derived GPIIb and GPIIIa sequences from HEL cells, but megakaryocyte-specific sequences were undetermined.

Purpose of the Study:

  • To isolate and characterize full-length complementary DNAs (cDNAs) for GPIIb and GPIIIa directly from human megakaryocytes.
  • To compare these megakaryocyte-derived sequences with those previously obtained from HEL cells and endothelial cells.
  • To identify any nucleotide differences that may impact protein structure and function.

Main Methods:

  • Isolation of megakaryocyte cDNA libraries.
  • Sequencing of full-length cDNAs for GPIIb and GPIIIa.
  • Comparative sequence analysis between megakaryocyte, HEL cell, and endothelial cell cDNAs.
  • Analysis of messenger RNA (mRNA) sizes for GPIIb and GPIIIa.

Main Results:

  • Full-length cDNAs for megakaryocyte GPIIb and GPIIIa were successfully isolated.
  • Nucleotide sequence variations were identified in GPIIIa cDNAs between megakaryocytes, HEL cells, and endothelial cells.
  • A specific nucleotide difference at position 633 in GPIIb was noted, with cysteine in megakaryocytes and serine in HEL cells.
  • mRNA species for GPIIb (3.4 kb) and GPIIIa (6.1 kb) exhibited identical sizes in both HEL cells and human megakaryocytes.

Conclusions:

  • This study provides the definitive sequences for GPIIb and GPIIIa as produced by human megakaryocytes.
  • Identified nucleotide differences highlight potential variations in platelet glycoprotein structure and function depending on the cell source.
  • The findings contribute to a deeper understanding of platelet glycoprotein synthesis and genetic diversity.

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