GRASP65 controls the cis Golgi integrity in vivo

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• GRASP65 and GRASP55 are peripheral Golgi proteins involved in Golgi structure and protein transport.
• They play roles in stacking Golgi cisternae and forming the Golgi ribbon.

Purpose of the Study:

• To investigate the essentiality of GRASP65 for organism viability and Golgi function.
• To elucidate the specific role of GRASP65 in cis Golgi network continuity.

Main Methods:

• Generation of a GRASP65-deficient mouse model using homologous recombination.
• Analysis of tissue, cellular, and subcellular organization in GRASP65 knockout mice.
• Fluorescence recovery after photobleaching (FRAP) assays to assess Golgi membrane network dynamics.
• Lectins staining to evaluate glycosylation changes.

Main Results:

• GRASP65-deficient mice were healthy, fertile, and showed no gross defects in tissue or cellular organization.
• Despite a normal Golgi ribbon appearance, FRAP assays revealed functional discontinuities in the cis cisternal membrane network.
• Significant alterations in plasma membrane GSII lectin staining were observed in mutant tissues.

Conclusions:

• GRASP65 is essential for maintaining cis Golgi network continuity, which is critical for proper glycosylation.
• Neither GRASP65 nor the continuity of the cis Golgi network are indispensable for the survival of a complex organism.