Identification and characterization of an isoform of murine Mpl.
A new isoform of the full-length murine thrombopoietin (Tpo) receptor was isolated from a murine spleen cDNA library. This isoform, c-mpl-II, differs from full-length c-mpl (c-mpl-I) by virtue of deletion of 180 nucleotides that encode 60 amino acids located in the extracellular domain of Mpl. Normal murine megakaryocytes were found to express both c-mpl-I and c-mpl-II transcripts. BaF3 cells transfected with c-mpl-I expressed a 95 kDa protein that was displayed on the cell surface and bound 125I-Tpo. BaF3 cells transfected with c-mpl-II expressed a 70 kDa protein. However, these cells were not able to bind 125I-Tpo and surface display of Mpl-II could not be detected. In summary, c-mpl-II is an isoform of murine Mpl expressed by megakaryocytes that lacks a 60 amino acid region required for surface expression of the protein.
Sabath
Diana F
DF
Department of Medicine, University of Washington, Harborview Medical Center, 325 Ninth Ave, Box 359756, Seattle, WA 98104, USA.
Lofton-Day
Cathy
C
Lin
Nancy
N
Lok
Si
S
Kaushansky
Kenneth
K
Broudy
Virginia C
VC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D015723:Gene Library; D008533:Megakaryocytes / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins; D020033:Protein Isoforms / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000302:isolation & purification; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D013154:Spleen / Q000378:metabolism; D014162:Transfection
D018076:DNA, Complementary; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; C082218:MPL protein, human