Biology Reference
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Uniform
concentration
Desensitization/
internalization
Chemoattractant
gradient
Actin assembly
Figure 8.1 Model for
-arrestin regulation of receptor turnover and actin assembly.
At the top of a chemoattractant gradient, the cell will be surrounded, thus experienc-
ing a uniform concentration. At
b
-arrestin-mediated
desensitization and internalization aid in receptor turnover. As the cell moves toward
a gradient, the concentration of agonist is lower and only receptors closest to the
gradient will be activated. At these concentrations,
b
-arrestin-mediated actin assembly
dominates, allowing the cell to move toward the source of the chemoattractant.
these high concentrations,
b
have been shown to require
b
-arrestins, both for receptor internalization and
for chemotaxis. Furthermore, chemokines oligomerize and the oligomers
can signal in a fashion distinct from the monomers, which can affect the
receptor response. Both of these features factor into
b
-arrestin-dependent
gradient sensing.
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