بررسي بازگشت پروتيينها از دستگاه گلژي به شبكه آندوپالسمي در سلولهاي هيبريدوماي موش‌

Study of the retrograde transport of proteins to the endoplasmic reticulum in mouse hybridoma cells

Vesicular transport is the predominant mechanism for exchange of proteins between membrane-bound organelles in eukaryotic cells. COP-coated vesicles are transport intermediates of the early secretory pathway. COPII-coated vesicles emerge from the endoplasmic reticulum (ER) in order to export proteins towards the Golgi complex. COPI-coated vesicles instead appear to be involved in both antrograde and retrograde transport within the Golgi, as well as mediating the recycling of proteins to the ER. Using cryosectioning and immunogold labeling of mouse hybridoma cells, the in situ distribution of one subgroup of COPI-coated vesicles, one retrograde-targeted molecule (KDEL receptor) as well as cargo headed in antrograde direction (monoclonal antibodies against MAP-2) were mapped. Electron microscope immunocytochemistry reveals that this subgroup of COPI-coated vesicle is present mainly in the pre-Golgi compartment and cis-face of the Golgi stacks. When double labeled with KDEL receptor-antibodies, coat-antibodies labeled clearly the same population of vesicles and pre-Golgi elements. Notably, analysis of double labeling for coat proteins and monoclonal antibody showed that positive pre-Golgi vesicles were not labeled for antrograde cargo. These findings establish a probable function of the studied population of COPI vesicles in the retrograde transport from the pre- and cis-Golgi to the ER.