The soluble form of urokinase receptor promotes angiogenesis through its Ser⁸⁸-Arg-Ser-Arg-Tyr⁹² chemotactic sequence.
BACKGROUND
The urokinase plasminogen activator receptor (u-PAR) focuses the proteolytic activity of the urokinase plasminogen activator (u-PA) on the endothelial cell surface, thus promoting angiogenesis in a protease-dependent manner. The u-PAR may exist in a glycophosphatidylinositol-anchored and in a soluble form (soluble u-PAR [Su-PAR]), both including the chemotactic Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² internal sequence.


OBJECTIVE
To investigate whether Su-PAR may trigger endothelial cell signaling leading to new vessel formation through its chemotactic Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² sequence.


RESULTS
In this study, the formation of vascular-like structures by human umbilical vein endothelial cells was assessed by using a matrigel basement membrane preparation. First, we found that Su-PAR protein promotes the formation of cord-like structures, and that this ability is retained by the isolated Ser(88) -Arg-Ser-Arg-Tyr⁹² chemotactic sequence, the maximal effect being reached at 10 nmol L⁻¹ SRSRY peptide (SRSRY). This effect is mediated by the α(v) β₃ vitronectin receptor, is independent of u-PA proteolytic activity, and involves the internalization of the G-protein-coupled formyl-peptide receptor in endothelial cells. Furthermore, exposure of human saphenous vein rings to Su-PAR or SRSRY leads to a remarkable degree of sprouting. Finally, we show that Su-PAR and SRSRY promote a marked response in angioreactors implanted into the dorsal flank of nude mice, retaining 91% and 66%, respectively, of the angiogenic response generated by a mixture of vascular endothelial growth factor and fibroblast growth factor type 2.


CONCLUSIONS
Our results show a new protease-independent activity of Su-PAR that stimulates in vivo angiogenesis through its Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² chemotactic sequence.
Bifulco
K
K
Department of Experimental Oncology, National Cancer Institute of Naples, Naples, Italy.
Longanesi-Cattani
I
I
Gala
M
M
DI Carluccio
G
G
Masucci
M T
MT
Pavone
V
V
Lista
L
L
Arra
C
C
Stoppelli
M P
MP
Carriero
M V
MV
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002633:Chemotaxis; D018920:Coculture Techniques; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D018919:Neovascularization, Physiologic / Q000502:physiology*; D055293:Receptors, Urokinase Plasminogen Activator / Q000737:chemistry / Q000502:physiology*; D015398:Signal Transduction; D012995:Solubility
D055293:Receptors, Urokinase Plasminogen Activator