Regulation of Golgi structure and function by signal transduction molecules

San Pietro, Enrica (2007). Regulation of Golgi structure and function by signal transduction molecules. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000fa45

Abstract

The Golgi complex is a highly organized and morphologically complicated intracellular organelle that serves as the crossroad of membrane trafficking. It has been demonstrated that membranous tubules connecting cistemae within Golgi stacks represent essential element the Golgi complex in mammalian cells (Marsh et al., 2004; Trucco et al., 2004). In spite of extensive morphological characterization two main questions have to be addressed: (i) which is the functional role and (ii) which is the molecular mechanisms behind the formation of such Golgi tubules?

It has recently been shown that these tubular connections are traffic dependent, suggesting that they might be involved in intra-Golgi transport (Marsh et al., 2004; Trucco et al., 2004). Moreover, cytosolic phospholipase A₂ (cPLA₂) enzymes (Six and Dennis, 2000) have been proposed to modify the lipid membrane conformation favouring membrane curvature and thus promoting the formation of such tubular structures (de Figueiredo et al., 1998).

This study shows that upon activation of secretory transport, cytosolic PLA₂α (cPLA₂α) is rapidly recruited to the Golgi and is required for the formation of tubular connections linking different Golgi sub-compartments. In contrast, cPLA₂α does not control the dynamic of Golgi vesicles. Importantly, by blocking cPLA₂α and thus the formation of Golgi tubules the progression of cargo is arrested at the cis level of the Golgi stacks; while the recovery of cPLA₂α activity results in the re-formation of Golgi tubular structures and in the reactivation of transport through the Golgi complex. These findings indicate that tubular connections regulated by cPLA₂α are essential mediators of intra-Golgi traffic.