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Thrombomucin, a novel cell surface protein that defines thrombocytes and multipotent hematopoietic progenitors.

ABSTRACT: MEP21 is an avian antigen specifically expressed on the surface of Myb-Ets-transformed multipotent hematopoietic precursors (MEPs) and of normal thrombocytes. Using nanoelectrospray tandem mass spectrometry, we have sequenced and subsequently cloned the MEP21 cDNA and named the gene thrombomucin as it encodes a 571-amino acid protein with an extracellular domain typical of the mucin family of proteoglycans. Thrombomucin is distantly related to CD34, the best characterized and most used human hematopoietic stem cell marker. It is also highly homologous in its transmembrane/intracellular domain to podocalyxinlike protein-1, a rabbit cell surface glycoprotein of kidney podocytes. Single cell analysis of yolk sac cells from 3-d-old chick embryos revealed that thrombomucin is expressed on the surface of both lineage-restricted and multipotent progenitors. In the bone marrow, thrombomucin is also expressed on mono- and multipotent progenitors, showing an overlapping but distinct expression pattern from that of the receptor-type stem cell marker c-kit. These observations strengthen the notion that the Myb-Ets oncoprotein can induce the proliferation of thrombomucin-positive hematopoietic progenitors that have retained the capacity to differentiate along multiple lineages. They also suggest that thrombomucin and CD34 form a family of stem cell-specific proteins with possibly overlapping functions in early hematopoietic progenitors.

SUBMITTER: McNagny KM

PROVIDER: S-EPMC2132552 | biostudies-literature | 1997 Sep

REPOSITORIES: biostudies-literature

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Thrombomucin, a novel cell surface protein that defines thrombocytes and multipotent hematopoietic progenitors.

McNagny K M KM Pettersson I I Rossi F F Flamme I I Shevchenko A A Mann M M Graf T T

The Journal of cell biology 19970901 6

MEP21 is an avian antigen specifically expressed on the surface of Myb-Ets-transformed multipotent hematopoietic precursors (MEPs) and of normal thrombocytes. Using nanoelectrospray tandem mass spectrometry, we have sequenced and subsequently cloned the MEP21 cDNA and named the gene thrombomucin as it encodes a 571-amino acid protein with an extracellular domain typical of the mucin family of proteoglycans. Thrombomucin is distantly related to CD34, the best characterized and most used human hem ...[more]

PMID: 9298993

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Project description:Regenerative tissues such as the skin epidermis, the intestinal mucosa or the hematopoietic system are organized in a hierarchical manner with stem cells building the top of this hierarchy. Somatic stem cells harbor the highest self-renewal activity and generate a series of multipotent progenitors which differentiate into lineage committed progenitors and subsequently mature cells. In this report, we applied an in-depth quantitative proteomic approach to analyze and compare the full proteomes of ex vivo isolated and FACS-sorted populations highly enriched for either multipotent hematopoietic stem/progenitor cells (HSPCs, Lin(neg)Sca-1(+)c-Kit(+)) or myeloid committed precursors (Lin(neg)Sca-1(-)c-Kit(+)). By employing stable isotope dimethyl labeling and high-resolution mass spectrometry, more than 5000 proteins were quantified. From biological triplicate experiments subjected to rigorous statistical evaluation, 893 proteins were found differentially expressed between multipotent and myeloid committed cells. The differential protein content in these cell populations points to a distinct structural organization of the cytoskeleton including remodeling activity. In addition, we found a marked difference in the expression of metabolic enzymes, including a clear shift of specific protein isoforms of the glycolytic pathway. Proteins involved in translation showed a collective higher expression in myeloid progenitors, indicating an increased translational activity. Strikingly, the data uncover a unique signature related to immune defense mechanisms, centering on the RIG-I and type-1 interferon response systems, which are installed in multipotent progenitors but not evident in myeloid committed cells. This suggests that specific, and so far unrecognized, mechanisms protect these immature cells before they mature. In conclusion, this study indicates that the transition of hematopoietic stem/progenitors toward myeloid commitment is accompanied by a profound change in processing of cellular resources, adding novel insights into the molecular mechanisms at the interface between multipotency and lineage commitment.

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Thrombomucin, a novel cell surface protein that defines thrombocytes and multipotent hematopoietic progenitors.

Publications

Thrombomucin, a novel cell surface protein that defines thrombocytes and multipotent hematopoietic progenitors.

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