Division of the intermediate compartment at the onset of mitosis provides a mechanism for Golgi inheritance

Abstract

SummaryAs mammalian cells prepare for mitosis, the Golgi ribbon is first unlinked into its constituent stacks and then transformed into spindleassociated, pleiomorphic membrane clusters in a process that remains enigmatic. Also, it remains unclear whether Golgi inheritance involves the incorporation of Golgi enzymes into a pool of coat protein I (COPI) vesicles, or their COPI-independent transfer to the endoplasmic reticulum (ER). Based on the observation that the intermediate compartment (IC) at the ER-Golgi boundary is connected to the centrosome, we examined its mitotic fate and possible role in Golgi breakdown. The use of multiple imaging techniques and markers revealed that the IC elements persist during the M phase, maintain their compositional and structural properties and remain associated with the mitotic spindle, forming circular arrays at the spindle poles. At G2/M transition, the movement of the pericentrosomal domain of the IC (pcIC) to the cell centre and its expansion coincide with the unlinking of the Golgi ribbon. At prophase, coupled to centrosome separation, the pcIC divides together with recycling endosomes, providing novel landmarks for mitotic entry. We provide evidence that the permanent IC elements function as way stations during the COPI-dependent dispersal of Golgi components at prometa-and metaphase, indicating that they correspond to the previously described Golgi clusters. In addition, they continue to communicate with the vesicular 'Golgi haze' and thus are likely to provide templates for Golgi reassembly. These results implicate the IC in mitotic Golgi inheritance, resulting in a model that integrates key features of the two previously proposed pathways.

Mitotic inheritance of the Golgi complex and its role in cell division

“…An additional theory supports the view that Golgi membranes are redistributed into the ER during mitosis (Sengupta et al., ). Of note, the intermediate compartment and part of the Golgi matrix proteins are physically associated with the spindle poles during mitosis (Seemann et al., ; Marie et al., ), suggesting that this represents a mechanism for the correct inheritance of proteins that are involved in Golgi reformation at mitosis exit.…”

Intermediate Compartment: A Sorting Station between the Endoplasmic Reticulum and the Golgi Apparatus

“…Accordingly, the IC has been proposed to constitute a dynamic, but stable membrane network due to its anchoring next to the ERES and the centrosome Figure 7(c)). This model is supported by studies of mitotic cells, showing that the IC persists despite Golgi breakdown and the rearrangement of the MTs, and maintains its spatial organization due to its ongoing association with the spindle MTs and the centrosomes at the spindle poles (Marie et al, 2012; Figure 3(a)).…”

“…Both interact with multiple effectors suggesting that they coordinate successive transport steps (Barnekow et al, 2009). The association of Rab1 with the cytoplasmic surface of IC and cis-Golgi membranes, and its absence from the ER, has been demonstrated by EM Saraste et al, 1995;Satoh et al, 2003;Marie et al, 2012; Figure 2). The two Rab1 isoforms, Rab1A and RAB1B (93% homology), are recruited to IC membranes at ERES, show similar localizations by LM (Mochizuki et al, 2013; Figure 3(a)), but seem to play distinct roles in tubular and vesicular (long and short range) trafficking within the IC.…”

“…Nu * * * * phosphorylated at mitosis (Bailly et al, 1991), correlating with the cessation of tubular IC dynamics, whereas COPI-mediated vesicular transport continues (Marie et al, 2012). Rab1A can functionally replace Ypt1, which coordinates two-way ER-Golgi trafficking in the yeast Saccharomyces cerevisiae (Haubruck et al 1989;Segev, 2001;Kamena et al, 2008).…”

“…Visualization of IC dynamics using GFP-Rab1A showed that the pleiomorphic transport carriers arriving along MTs from the cell periphery do not move directly to cis-Golgi, but are targeted to the MTOC/centrosome that is normally positioned next to the Golgi ribbon. In cells displaying centrosome motility, for example, cells that are migrating or entering mitosis, the centrosome-targeted membranes can be resolved as a separate compartment, called the pericentrosomal IC (pcIC), which is distinct from the cis-Golgi-adjacent IC domain (Marie et al, , 2012Mochizuki et al, 2013; Figure 3(a)). Live imaging further showed that the separated pcIC and the Golgi communicate via tubular and globular carriers.…”