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Golgi proteins sort by the space available inside membrane sacs

Long protein extensions accumulated at the edges of Golgi membrane sacs in a peer-reviewed cell study. Shortening those extensions shifted proteins toward the interior. Imaging and experiments that widened another membrane compartment support a geometric role in protein placement. Most experiments used cultured cells, and the mechanism concerns a selected class of membrane proteins.

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Generated grayscale microscopy imagery shows stacked Golgi membrane sacs with narrow central spaces and wider rounded rims.

Shorter protein extensions enter the interior

Shortening a protein extension changed where it settled within the Golgi apparatus, the cellular stack of flattened membrane sacs that processes and transports proteins. In one peer-reviewed study, researchers compared GPP130, a membrane protein concentrated at the sacs’ edges, with a differently distributed protein. The researchers altered and shortened its inward-projecting segment, increasing GPP130’s presence in the interior.[1]

Long coiled segments made from different sequences still supported edge enrichment. Two other Golgi proteins with long coils showed similar distributions. HeLa culture cells provided the main experimental setting; additional cell lines supplied selected comparisons.[1]

Imaging reveals a narrow enclosed space

Cryo-electron tomography, which reconstructs three-dimensional structures from frozen samples, found narrow spaces inside Golgi sacs. Some were smaller than the predicted length of the extended protein segment. The Golgi measurements came from one cell. The more spacious edges offered a different geometry from the flattened interiors.[1]

Widening a membrane gap increases protein access

Researchers also redirected proteins to other cellular membrane compartments. Increasing the gap between the two nuclear membranes experimentally allowed a long-domain protein greater access. They linked this result to the space available for the extension. Lipids, membrane curvature and protein interactions may also contribute to positioning; the tested length-dependent mechanism concerns a particular membrane-protein class.[1]

References

  1. News sourceNature CommunicationsInterior space helps determine where Golgi proteins settle↩1↩2↩3↩4
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