Photoactivation of GFP reveals protein dynamics within the endoplasmic reticulum membrane.
Components of the plant cell secretory pathway, including the endoplasmic reticulum and Golgi apparatus, are in constant motion. The photoactivation of GFP has been used to determine that proteins within the membrane of the ER flow as the ER is remodelled. Measurement of the rate at which activated GFP moves away from the activation spot shows that this motion is much faster than would be expected if membrane components moved simply by diffusion. Treatment with latrunculin to depolymerize the actin cytoskeleton stops ER remodelling and reduces the rate of GFP movement to that expected from diffusion alone. This suggests that myosin binds directly or indirectly to ER membrane proteins and actively moves them around over the actin scaffold. Tracking of Golgi body movement was used to demonstrate that they move at the same rate and in the same direction as do photoactivated ER surface proteins. Golgi bodies, therefore, move with, and not over, the surface of the ER. These observations support the current theory of continuity between Golgi bodies and discrete ER exit sites in the ER membrane.
Runions
John
J
Biological and Molecular Sciences, Oxford Brookes University, Oxford OX3 0BP, UK. jrunions@brookes.ac.uk
Brach
Thorsten
T
Kühner
Sebastian
S
Hawes
Chris
C
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000502:physiology*; D006056:Golgi Apparatus / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D007425:Intracellular Membranes / Q000502:physiology*; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000378:metabolism*; D009068:Movement; D010777:Photochemistry; D012984:Software; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014026:Nicotiana
D019086:Bridged Bicyclo Compounds, Heterocyclic; D008565:Membrane Proteins; D013844:Thiazoles; D053778:Thiazolidines; D049452:Green Fluorescent Proteins; C037068:latrunculin B