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Study of ceruloplasmin (CP) and the iron exporter ferroportin (FPN) in human lymphocytes and monocytes
Author(s) -
Costa Luciana,
Marques Liliana,
Banha Joao,
Willemetz Alexandra,
CaneHergaux François
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.240
Subject(s) - ceruloplasmin , u937 cell , western blot , ferroportin , cytosol , immunofluorescence , microbiology and biotechnology , blot , chemistry , cell , monocyte , cell culture , northern blot , biology , gene expression , biochemistry , antibody , gene , enzyme , apoptosis , immunology , genetics , iron homeostasis
Ferroxidase activity by multicopper oxidases such as CP is required for the stability on cell surface of the iron exporter FPN and, consequently, for iron efflux from mammalian cells. In different cell types, CP is expressed as a secreted (sCP) and/or as a membrane glycosylphosphatidylinositol‐anchored isoform (GPI‐CP). Recently, we have reported the transcriptional expression of both sCP and GPI‐ CP isoforms in human peripheral blood lymphocytes (huPBL). Here we study FPN and CP expression at both mRNA (RT‐PCR) and protein (Western blotting and immunofluorescence) levels in these cells as well as in human peripheral blood monocytes (huPBM) and human monocytic cell lines (THP‐1 and U937). By western blot, CP was detected in both membrane (159 kDa) and cytosol (134 kDa) extracts of huPBL. The cytosol associated form present the same molecular weight as plasma CP (sCP). The membrane associated form likely corresponds to GPI‐CP. Indeed, treatment with PI‐PLC, an enzyme that cleaves specifically GPI‐anchored proteins, induces a significant decrease in ceruloplasmin expression at huPBL surface. Interestingly, FPN presents similar expression at the cell surface of huPBL. In addition, FACS analysis and immunofluorescence studies showed the expression of CP at the surface of huPBM. Experiments are in progress to clarify the relation of these two proteins in human mononuclear cells iron efflux.