Effect of preferential insertion of LDL receptors near coated pits |
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Authors: | Carla Wofsy Hector Echavarría-Heras Byron Goldstein |
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Institution: | (1) Department of Mathematics and Statistics, University of New Mexico, 87131 Albuquerque, New Mexico;(2) Theoretical Division, Los Alamos National Laboratory, University of California, 87545 Los Alamos, New Mexico |
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Abstract: | Recent experiments suggest that low density lipoprotein (LDL) receptors on human fibroblasts are not inserted into the plasma
membrane uniformly, as earlier experiments indicated, but are inserted into specialized regions, called plaques, where coated
pits form. If the consequent reduction in the time required for LDL receptors to diffuse to coated pits were significant,
this could alter conclusions drawn from previous calculations based on the assumption that LDL receptors are inserted uniformly.
In particular, the conclusion could be wrong that diffusion of LDL receptors to coated pits is the rate limiting step in the
interaction of cell surface LDL receptors with coated pits. Here we calculate the extent of the reduction in mean travel time
of an LDL receptor to a coated pit, as a function of the plaque radius. We find that only if LDL receptor insertion is limited
to a very small portion of the plasma membrane near coated pit sites is there a substantial decrease in the average time it
would take an LDL receptor to diffuse to a coated pit. In order for preferential insertion of LDL receptors into plaques to
cut the mean receptor travel time in half, plaques would have to take up no more than 10% of the cell surface area; to reduce
the travel time by a factor of 10 plaques would have to cover only 2% of the cell surface, approximately twice the area covered
by coated pits at 37°C. |
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Keywords: | Low density lipoprotein receptors effect of preferential insertion near coated pits lipoprotein receptors effect of preferential insertion near coated pits coated pits effect of preferential insertion of LDL receptors near receptors effect of preferential insertion near coated pits |
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