Golgi enlargement in Arf-depleted yeast cells is due to altered dynamics of cisternal maturation

Abstract

Regulation of the size and abundance of membrane compartments is a fundamental cellular activity. In Saccharomyces cerevisiae, disruption of the ADP-ribosylation factor 1 (ARF1) gene yields larger and fewer Golgi cisternae by partially depleting the Arf GTPase. We observed a similar phenotype with a thermosensitive mutation in Nmt1, which myristoylates and activates Arf. Therefore, partial depletion of Arf is a convenient tool for dissecting mechanisms that regulate Golgi structure. We found that in arf1D cells, late Golgi structure is particularly abnormal, with the number of late Golgi cisternae being severely reduced. This effect can be explained by selective changes in cisternal maturation kinetics. The arf1D mutation causes early Golgi cisternae to mature more slowly and less frequently, but does not alter the maturation of late Golgi cisternae. These changes quantitatively explain why late Golgi cisternae are fewer in number and correspondingly larger. With a stacked Golgi, similar changes in maturation kinetics could be used by the cell to modulate the number of cisternae per stack. Thus, the rates of processes that transform a maturing compartment can determine compartmental size and copy number.

Traffic Through the Trans-Golgi Network and the Endosomal System Requires Collaboration Between Exomer and Clathrin Adaptors in Fission Yeast

“…Aberrant Golgi morphology has been observed under conditions that alter ER to Golgi traffic and traffic through and from the Golgi, probably because of a disequilibrium between protein and lipid input and output ratios (Ward et al 2001;Bhave et al 2014;Papanikou et al 2015). We have found physical and functional interaction between exomer and AP-1, but not between exomer and COPI and COPII.…”

Molecular Dissection of Mycobacterium tuberculosis Integration Host Factor Reveals Novel Insights into the Mode of DNA Binding and Nucleoid Compaction

“…Three-dimensional reconstructions were done by weighted back projection of aligned images. Tomographic reconstructions thus obtained were processed as described (45).…”

Intracellular Scaling Mechanisms

“…Cargo influx and efflux occurs through vesicular traffic, meaning that membranes are constantly being added to and removed from the Golgi. Not surprisingly, Golgi cisternae size is dependent on this flux balance, and altering of trafficking pathways can lead to significant changes in Golgi size (Bevis et al 2002;Bhave et al 2014). Thus, Golgi size regulation could be considered a variant of the dynamic balance mechanisms discussed previously, only in this case with the balance point set by demand-dependent flux rates into and out of the Golgi cisternae.…”