Golgi complex: Stacking the cisternae

Stacks of disc-shaped cisternal membranes are a defining feature of the Golgi complex. Secretory products move through the stack from the ‘cis’ cisternae — which receives cargo from the endoplasmic reticulum (ER) — to the ‘trans’ cisternae on the opposite side, and most Golgilocalized proteins are targeted to the cis, medial or trans subcompartments. The efficient processing of secretory proteins and lipids by Golgi enzymes depends on vesicle transport, regardless of whether the secretory cargo actually moves through the stack by vesicle transport, or whether it moves by cisternal maturation as some believe. It is therefore assumed, though not proven, that stack formation increases processing efficiency by decreasing the distances through which vesicles have to be transported. Vesicles are most abundant at the highly fenestrated rims of the cisternae, while compact stacking is most evident at the cisternal cores. In vertebrates, continuities of cisternal membranes in the rim region serve to link adjacent Golgi stacks, forming a ribbon of stacked membranes. Remarkably, in these cells, the linked Golgi stack is completely disassembled and reassembled every cell division to allow accurate Golgi inheritance by the daughter cells. What are the molecular processes that underlie the stacking of the Golgi cisternae?