Hematopoietic stem and progenitor cell mobilization in mice and humans by a first-in-class mirror-image oligonucleotide inhibitor of CXCL12.

NOX-A12 is a PEGylated mirror-image oligonucleotide (a so-called Spiegelmer) that binds to CXCL12 (stromal cell-derived factor-1, SDF-1) with high affinity thereby inhibiting CXCL12 signaling on both its receptors, CXCR4 and CXCR7. In animals, NOX-A12 mobilized white blood cells (WBCs) and hematopoietic stem and progenitor cells (HSCs) into peripheral blood (PB). In healthy volunteers, single doses of NOX-A12 had a benign safety profile and also dose-dependently mobilized WBCs and HSCs into PB. HSC peak mobilization reached a plateau at five times the baseline level at an i.v. dose of 5.4 mg/kg. In accordance with the plasma half-life of 38 h, the duration of the WBC and HSC mobilization was long lasting and increased dose-dependently to more than 4 days at the highest dose (10.8 mg/kg). In conclusion, NOX-A12 may be appropriate for therapeutic use in and beyond mobilization of HSCs, e.g., in long-lasting mobilization and chemosensitization of hematological cancer cells.

alpha1 Integrin cytoplasmic domain is involved in focal adhesion formation via association with intracellular proteins.

Integrins are heterodimeric adhesion receptors consisting of alpha- and beta-subunits capable of binding extracellular matrix molecules as well as other adhesion receptors on neighbouring cells. These interactions induce various signal transduction pathways in many cell types, leading to cytoskeletal reorganization, phosphorylation and induction of gene expression. Integrin ligation leads to cytoplasmic protein-protein interactions requiring both integrin cytoplasmic domains, and these domains are initiation points for focal adhesion formation and subsequent signal transduction cascades. In previous studies we have shown that the very short cytoplasmic alpha1 tail is required for post-ligand events, such as cell spreading as well as actin stress-fibre formation. In the present paper we report that cells lacking the cytoplasmic domain of the alpha1 integrin subunit are unable to form proper focal adhesions and that phosphorylation on tyrosine residues of focal adhesion components is reduced on alpha1beta1-specific substrates. The alpha1 cytoplasmic sequence is a specific recognition site for focal adhesion components like paxillin, talin, alpha-actinin and pp125FAK. It seems to account for alpha1-specific signalling, since when peptides that mimic the cytoplasmic domain of alpha1 are transferred into cells, they influence alpha1beta1-specific adhesion, presumably by competing for binding partners. For alpha1 integrin/protein binding, the conserved Lys-Ile-Gly-Phe-Phe-Lys-Arg motif and, in particular, the two lysine residues, are important.

The cytoplasmic domain of the alpha1 integrin subunit influences stress fiber formation via the conserved GFFKR motif.

Integrins are heterodimeric transmembrane proteins that mediate substrate adhesion and migration but also the bidirectional transfer of information across the plasma membrane via their cytoplasmic domains. We addressed the question of whether the very short cytoplasmic tail of the alpha1 integrin subunit of alpha1beta1 integrin is required for alpha1beta1-specific adhesion, spreading, and migration. For this purpose we transfected the alpha1 integrin subunit and two cytoplasmically truncated alpha1 subunits into Chinese hamster ovary (CHO) cells. Elimination of the entire cytoplasmic domain of the alpha1 subunit does not affect adhesion but leads to inhibition of spreading and stress fiber formation. The defect in spreading could not be rescued by lysophosphatidic acid, which has been reported to stimulate actin stress fiber formation via Rho. Additionally, deletion of the entire cytoplasmic domain of the alpha1 subunit abolishes migration toward alpha1beta1-specific substrates. Migration and stress fiber formation are similar in CHO-alpha1 cells and CHO cells carrying an alpha1 subunit still containing the conserved GFFKR motif. So, the GFFKR motif of the alpha1 subunit is essential and sufficient for these processes.