It seems only logical that there would be a mechanism for guiding blood vessel growth, he adds. Though at first glance, blood vessels appear less intricate than neuronal circuits--mere plumbing to carry blood, one might think--they do form an exquisite structure that is largely identical in all people. What is behind this order?
In the current study, Klagsbrun's team reports initial experiments asking in a simple way whether neuropilin somehow affects the way blood vessels move. They engineered endothelial cells to contain either neuropilin, a long-known VEGF receptor called KDR, or both and then measured how avidly the cells were migrating up a gradient of VEGF. They found that, indeed, neuropilin more than doubled this chemotactic response of the cells, but only if they also expressed KDR.
This suggests that neuropilin might impart a sense of direction to the growth of capillaries, but does so by acting in conjunction with another receptor. This finding jibes with a growing notion among molecular biologists that receptors often work in pairs and that it is the particular combination of individual receptor molecules mediating a given signal that defines a cell's specific response.
Many other questions remain, such as how far the two systems overlap. In
collaboration with Johnathan Raper of the University of Pennsylvania, who
codiscovered the collapsin/semaphorins, Klagsbrun is now testing whether VEGF
acts on neurons or whether semaphorin acts on endothelial cells, which carry
neuropilin. If semaphorin turned out to inhibit endothelial cell movement, much
like it repels neurons, he says, it might become a candidate angi
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Contact: Peta Gillyatt
pgillyat@warren.med.harvard.edu
617-432-0443
Harvard Medical School
20-Mar-1998