Abstract
It is becoming increasingly accepted that together with vesicles, tubules play a major role in the transfer of cargo between different cellular compartments. In contrast to our understanding of the molecular mechanisms of vesicular transport, little is known about tubular transport. How signal transduction molecules regulate these two modes of membrane transport processes is also poorly understood. In this study we investigated whether protein kinase A (PKA) activity regulates the retrograde, tubular transport of Golgi matrix proteins from the Golgi to the endoplasmic reticulum (ER). We found that Golgi-to-ER retrograde transport of the Golgi matrix proteins giantin, GM130, GRASP55, GRASP65, and p115 was impaired in the presence of PKA inhibitors. In addition, we unexpectedly found accumulation of tubules containing both Golgi matrix proteins and resident Golgi transmembrane proteins. These tubules were still attached to the Golgi and were highly dynamic. Our data suggest that both fission and fusion of retrograde tubules are mechanisms regulated by PKA activity.
Highlights
Membrane trafficking along the endocytic and secretory pathways is a highly regulated process
In HeLa cells the retrograde transport of these Golgi proteins is blocked by the protein kinase inhibitor H-89 [34], suggesting that protein phosphorylation plays a role in tubulation at the Golgi-endoplasmic reticulum (ER) interface
We evaluated if the blockage of retrograde transport by H-89 occurs for cis- and medial Golgi matrix proteins
Summary
Membrane trafficking along the endocytic and secretory pathways is a highly regulated process. Co-incubation for 60 min with BFA and 30 μM H-89 resulted in complete blockage of the redistribution of GM130 and Man-II, similar to what has been shown in HeLa cells for GM130 and the type-II Golgi membrane protein GPP130 [34] (Fig 1D).
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