Studying The Structure Of Golgi Complex And Endoplasmic Reticulum By AFE

The Golgi complex and endoplasmic reticulum(ER) are key organelles of theendo-membrane system, locating at the classical secretory pathway. They possessdifferent structure and function, simultaneously, they are functionally related eachother, referring to protein synthesis, protein process and secretion, as well as thebiomembrane formation and transport. The study on molecular mechanisms of theGolgi complex and ER has been hot in the field of cell biology for quite a long timenow and in the future. Currently, the investigations of the Golgi complex and ER arecompleted mainly by the conventional EM, and the others technologies on its basisincluding3-D EM, EM tomography and so on. Their complex structure at themolecular level remains elusive due to limited approaches. In this experiment, weemployed high-resolution and in-situ AFM to directly observe these organelles at highresolution and obtained some research results shown as follows:（1）The structures of Golgi complex referring to the Golgi stack, cisternal structure,relevant tubules and vesicles are directly visualized by atomic force microscope(AFM). Meanwhile, we obtained some novel findings. High-resolution and in-situatomic force microscopy is employed to directly obtain the images on both sides ofthe Golgi membrane and confirm the existence of lipid rafts in the Golgi membranes.Our AFM results indicate that the outer leaflet of Golgi membranes is relativelysmooth with the average roughness in0.82±0.24nm; on the contrary, the innermembrane leaflet is rough covered by dense proteins with the average roughness in1.95±0.62nm. We used real-time AFM to investigate the effect of MβCD and TX-100on the inner membrane leaflet, and reveal that most of the lipid rafts in Golgimembranes are in the size range of20–200nm and appear irregular in shape.（2）The rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum(SER) presenting vesicle-like structures were directly imaged by AFM. Themagnifying images indicate the RER and SER structure in detail. The AFM resultsshow that the SER cisterna is comparatively inflated and convoluted, and the surfaceis smooth, on the contrary, the RER cisterna is relatively flat, and its surface isdistributed with some particles.In summary, this is the study using in-situ AFM to deeply investigate thestructure of the Golgi complex and endoplasmic reticulum(ER) at nanometer resolution under quasi-native conditions, and acquire valuable results. The results maybe significant to further reveal their respectively structure-function relationship andpave the way for the study of the biomembrane cycling system in living cells at themolecular level. Meanwhile, this study is good for researching the correlationbetween the Golgi complex and endoplasmic reticulum, providing a basis forinvestigating therapy methods on disease related with the Golgi complex andendoplasmic reticulum.