A conditional v-Rel estrogen receptor fusion protein, v-RelER, causes estrogen-dependent but otherwise unaltered v-rel-specific transformation of chicken bone marrow cells. Here, we demonstrate that such v-relER-transformed cells exhibit B lymphoid determinants in line with earlier studies on v-rel-transformed cells. However, following inactivation of v-RelER oncoprotein activity by administration of an estrogen antagonist, cells differentiate into antigen-presenting dendritic cells as judged by several morphological and functional criteria. Additionally, under yet different culture conditions, v-relER cells differentiate into cells resembling polymorphonuclear neutrophils. Our studies therefore suggest that the conditional v-RelER, and probably also the authentic v-Rel, transform a common progenitor for neutrophils and dendritic cells.
Dendritic cells are professional antigen presenting cells that capture antigens and migrate to lymphoid tissues to elicit specific T cell responses. Here we used an in vitro differentiation system for generating highly motile dendritic cells from chicken bone marrow progenitors by employing the conditional v-Rel estrogen receptor (ER) fusion protein v-RelER. Molecular mechanisms of dendritic cell motility were investigated. Differentiation of v-relER progenitors into dendritic cells is associated with a reduction in cell-cell and cell-extracellular matrix interactions as cells acquire motility. We demonstrate that v-relER progenitors and dendritic cells express several adhesion receptors and components of adhesion complexes. Differentiation of v-relER cells was accompanied by downregulation of focal adhesion kinase (FAK), a key molecule of adhesion complexes, but ectopic FAK expression did not affect cell adhesion and motility. Interestingly, v-relER dendritic cells exhibit a polarised expression pattern of actin and vimentin, with actin being highly concentrated at the leading edge of the cells where lamellipodia are formed. FAK, paxillin and tyrosine phosphorylated proteins are found at both poles of the cell and colocalise with actin at the leading edge, while surface beta1 integrin is confined to the uropod at the rear. CD34(+)stem cell-derived human dendritic cells also exhibited an elongated bipolar morphology, mode of migration and a polarised pattern of actin-vimentin expression similar to v-relER dendritic cells.
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