Haematopoietic stem cell differentiation promotes the release of prominin‐1/CD133‐containing membrane vesicles—a role of the endocytic–exocytic pathway

Abstract

The differentiation of stem cells is a fundamental process in cell biology and understanding its mechanism might open a new avenue for therapeutic strategies. Using an ex vivo co-culture system consisting of human primary haematopoietic stem and progenitor cells growing on multipotent mesenchymal stromal cells as a feeder cell layer, we describe here the exosome-mediated release of small membrane vesicles containing the stem and cancer stem cell marker prominin-1 (CD133) during haematopoietic cell differentiation. Surprisingly, this contrasts with the budding mechanism underlying the release of this cholesterol-binding protein from plasma membrane protrusions of neural progenitors. Nevertheless, in both progenitor cell types, protein–lipid assemblies might be the essential structural determinant in the release process of prominin-1. Collectively, these data support the concept that prominin-1-containing lipid rafts may host key determinants necessary to maintain stem cell properties and their quantitative reduction or loss may result in cellular differentiation.

CD133 is a modifier of hematopoietic progenitor frequencies but is dispensable for the maintenance of mouse hematopoietic stem cells

“…The direct interaction of mouse and human CD133 with membrane cholesterol is consistent with such scenario (19,47). Similarly, a fast turnover of CD133 at the cell surface might also lead to false negative, or its translocation to an internal pool and/or release by means of small membrane vesicles might account for such situation (23). Irrespective of its biological reasons, the lack of CD133 protein on the cell surface of murine HSCs, and lack of functional consequences on murine hematopoiesis in its absence, marks a substantial species difference between mouse and human and adds CD133 to the list of cell surface markers and cell-fate regulators that are not conserved across species (reviewed in ref.…”

“…Although the expression of Prom1 gene is observed at a transcriptional level by a sensitive method such as PCR, the absence of CD133 protein as monitored by flow cytometry might reflect numerous phenomena that are not mutually exclusive. In addition to a low level of expression and/or even the lack of translation, we could not exclude, for instance, an intracellular localization (e.g., endosomal compartment) of CD133 as recently reported in human HSCs and HPCs (23). Although the 13A4 epitope of mouse CD133 is independent of Nlinked sugar moieties (6), in contrast to the AC133 epitope of human CD133 (45), it could not be ruled out that it became embedded in cholesterol-based membrane microdomains impeding its immunodetection (reviewed in ref.…”

“…The level of complexity to understand the biological role of CD133 in stem cells has recently increased by the finding that small CD133-containing membrane vesicles can be released from human HSCs and neural stem cells during the differentiation process (23). Irrespective of the cellular mechanisms underlying the decrease or loss of CD133 (24), it has been proposed that CD133-containing membrane microdomains might act as stem cell-specific signal transduction platforms, and their reduction will somehow lead to cellular differentiation (23,25). In these contexts, whether CD133 itself is important for HSC fate decisions and/or for hematopoiesis in the mouse remains however unknown.…”

MicroRNAs are shaping the hematopoietic landscape

“…Such vesicles might be internalized by MSC feeder cells and miRNAs might thereby be further implicated in the crosstalk of stem cells with their niche. 91 There is also evidence that a significant fraction of extracellular miRNAs resides outside of vesicles 92 and that Ago2 complexes carry the extracellular circulating miRNAs independent of vesicles in human plasma. 93,94 However, whether these complexes are released on purpose with the aim of targeting specific cell surface receptors needs to be further investigated.…”

Prominin-1-Containing Membrane Vesicles: Origins, Formation, and Utility

“…By studying the cell biology of the stem cell antigen prominin-1 (CD133; see Chap. 1 ) in various cell types (epithelial and non-epithelial) including stem cells [ 12,13 ] , we have identi fi ed new classes of extracellular membrane vesicles, which have only been poorly characterized until now [14][15][16] . This chapter will focus on those that are distinctively labeled with prominin-1.…”