Protein sorting in the Golgi apparatus: a consequence of maturation and triggered sorting.
To explain how resident proteins distribute in peak-like patterns at various positions in the secretory pathway, Glick and co-workers postulated that resident proteins comprise different populations (termed kin populations) and that these compete with each other for entering retrograde transport carriers [Glick et al. (1997) FEBS Lett. 414, 177-181]. Using modelling and computer simulation, they could demonstrate that differences in competitiveness sufficed to generate overlapping but distinct peak-like steady state distributions of the different kin populations across the Golgi stack. In this study, we have tested the robustness of the competition model and find that over-expression or changes in the number of kin populations affect their overall steady state distributions. To increase the robustness of the system, we have introduced a milieu-induced trigger for recycling. This allows for a decrease in the coupling between kin populations permitting both over-expression as well as changes in the number of kin populations. We have also extended the model to include a Golgi to endoplasmic reticulum (ER) recycling pathway and find that only a small amount of resident proteins may recycle at any time without upsetting their observed distributions in the Golgi stack. The biological relevance of a trigger-induced sorting mechanism and ER recycling is discussed.
Weiss
M
M
MPI for FLuid Dynamics, Department of Nonlinear Dynamics, Göttingen, Germany. weiss@chaos.gwdg.de
Nilsson
T
T
D001667:Binding, Competitive; D022181:COP-Coated Vesicles / Q000378:metabolism; D003198:Computer Simulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D008954:Models, Biological; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D013269:Stochastic Processes; D021601:trans-Golgi Network / Q000378:metabolism
D011506:Proteins