Some geometrical considerations on membrane insertion by exocytosis.
A two-dimensional random walk model is used to describe constitutive exocytic transport. Specifically, the possibility of attaining selective vesicle insertion by purely geometrical effects is studied. The distribution of vesicle insertion on the membrane and the average time of translocation are determined as a function of Golgi apparatus size and position, cell morphology and size, walk bias due to cytoplasmic streaming or differential movement on microtubules, and steric effects caused by other organelles. The simulations suggest that significant selectivity in targeting can result from adequate Golgi positioning, in accordance with the hypothesis of Golgi reorientation by the microtubular network (Singer and Kupfer, 1986, Annu. Rev. Cell Biol. 2, 337-365). The selectivity in targeting also depends on the cellular morphology. Segregation of vesicle insertion can be obtained in the transport to the cellular front end and lateral membrane surfaces of a quadrilateral cell, thus suggesting a geometrical component in the exocytic transport in polarized cells.
Vits
H
H
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis 55455.
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D006056:Golgi Apparatus / Q000502:physiology; D008954:Models, Biological