Colocalization of the VEGF‐R2 and the common IL‐3/GM‐CSF receptor beta chain to lipid rafts leads to enhanced p38 activation

Abstract

Summary Previous studies suggested an important role for vascular endothelial growth factor (VEGF) and its receptors in postnatal haemopoiesis. However, it is unclear how VEGF receptor (VEGFR) signalling could interact with that issued from the activation of haematopoietic growth factor receptors. To elucidate this point we explored VEGF‐R2 and granulocyte‐macrophage colony‐stimulating factor receptor (GM‐CSFR) membrane localization and cell signalling in TF1‐KDR cells (TF1 leukaemic cells that overexpress VEGF‐R2/KDR). Activation of either GM‐CSFR or VEGF‐R2 was shown to determine the migration of both receptor elements (VEGF‐R2 and the common β‐chain of the GM‐CSFR) to lipid rafts. The study of receptor phosphorylation showed that GM‐CSF induced the phosphorylation of its own receptor and the transphosphorylation of VEGF‐R2; on the other hand, VEGF triggered the phosphorylation of its receptor and transphosphorylated the β‐chain of the GM‐CSFR. Co‐stimulation of TF1‐KDR cells with both GM‐CSF and VEGF‐A resulted in massive migration of both the common GM‐CSFR β‐chain and VEGF‐R2 to lipid rafts and sustained p38 mitogen‐activated protein kinase activation. Disruption of lipid rafts inhibited the capacity of both GM‐CSF and VEGF‐A to activate p38. Experiments with specific p38 inhibitors showed that p38 activation was required to sustain the VEGF‐ and GM‐CSF‐dependent proliferation of TF1‐KDR and the survival of primary acute myeloid leukaemia blasts.

Flipping the molecular switch for innate protection and repair of tissues: Long-lasting effects of a non-erythropoietic small peptide engineered from erythropoietin

“…Stress, e.g. by hypoxia or inflammation, induces a rapid (several minutes) movement to the cell surface (Bohr et al, 2015) with a likely coalescence into membrane rafts, as has been described for other heteroreceptors that utilize βcR (Saulle et al, 2009), and as has been described above for the EPOR dimer (McGraw et al, 2012). Assembly of the mature receptor would then allow for stimulation if hsEPO is available in the surrounding locale.…”

Induction of nitric oxide by erythropoietin is mediated by the β common receptor and requires interaction with VEGF receptor 2

“…53 In addition, there was a recent demonstration that erythropoietin activates nitric oxide synthase in murine erythroctyes via the PI3-K/Akt pathway. 54 The results presented suggest a novel interaction between VEGF-R2 and the ␤C-R that is necessary for VEGF or EPO to lead to an induction of NO.…”

The Receptor That Tames the Innate Immune Response

“…Because the self-assembly of type 1 cytokine receptors occurs in direct proportion to the probability of interaction within the membrane (that is, on the density of receptor subunits), the probability of formation of βCR-EPOR heteromers is presumably favored by a relative surplus of βCR. This assembly is enhanced within lipid rafts, specialized regions of the cell membrane in which the receptor subunits (for example, IL-3 and βCR), among other proteins, are concentrated (50). It is also known that the α receptor subunits that provide ligand specificity for other members of the type 1 cytokine receptor family increase the probability of complexing with βCR in the presence of the ligand (51,52).…”

“…Further, it is of interest to note that in other cellular systems, βCR has also been described as associated with VEGFR2. For example, the βCR of the IL-3 receptor was reported to associate with VEGFR2, specifically in lipid rafts (50). The βCR-EPOR was also recently shown to directly activate NF-κB, a key proinflammatory cytokine modulator, via a direct interaction with TNF receptor-associated factor 6 (TREAF6) (86).…”