title: Discrete, continuous, and stochastic models of protein sorting in the Golgi apparatus.
abstract: The Golgi apparatus plays a central role in processing and sorting proteins and lipids in eukaryotic cells. Golgi compartments constantly exchange material with each other and with other cellular components, allowing them to maintain and reform distinct identities despite dramatic changes in structure and size during cell division, development, and osmotic stress. We have developed three minimal models of membrane and protein exchange in the Golgi-a discrete, stochastic model, a continuous ordinary differential equation model, and a continuous stochastic differential equation model-each based on two fundamental mechanisms: vesicle-coat-mediated selective concentration of cargoes and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins during vesicle formation and SNARE-mediated selective fusion of vesicles. By exploring where the models differ, we hope to discover whether the discrete, stochastic nature of vesicle-mediated transport is likely to have appreciable functional consequences for the Golgi. All three models show similar ability to restore and maintain distinct identities over broad parameter ranges. They diverge, however, in conditions corresponding to collapse and reassembly of the Golgi. The results suggest that a continuum model provides a good description of Golgi maintenance but that considering the discrete nature of vesicle-based traffic is important to understanding assembly and disassembly of the Golgi. Experimental analysis validates a prediction of the models that altering guanine nucleotide exchange factor expression levels will modulate Golgi size.
authors.affiliation: Department of Physics, Carnegie Mellon University, Pennsylvania 15213, USA.
authors.forename: Haijun
authors.initials: H
authors.lastname: Gong
authors.forename: Yusong
authors.initials: Y
authors.lastname: Guo
authors.forename: Adam
authors.initials: A
authors.lastname: Linstedt
authors.forename: Russell
authors.initials: R
authors.lastname: Schwartz
mesh_terms: D000465:Algorithms; D018699:Coated Vesicles / Q000378:metabolism; D006056:Golgi Apparatus / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D021381:Protein Transport / Q000502:physiology*; D015203:Reproducibility of Results; D050600:SNARE Proteins / Q000378:metabolism; D013269:Stochastic Processes; D013997:Time Factors; D022161:Transport Vesicles / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D050600:SNARE Proteins