A Rab GTPase Is Required for Homotypic Assembly of the Endoplasmic Reticulum

Turner, Mark D.; Plutner, Helen; Balch, William E.

doi:10.1074/jbc.272.21.13479

Cited by 29 publications

(26 citation statements)

References 47 publications

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“…Another possible candidate required for ER tubule formation is Rab protein of small GTPase. The Rab protein has been reported to be required for ER assembly (Turner et al, 1997;Audhya et al, 2007). Interestingly, an Arabidopsis Rab protein, AtRab8, was found to interact with Arabidopsis reticulon family proteins, AtRTNLB1, -2, and -4 (Hwang and Gelvin, 2004).…”

Section: Gtp Hydrolysis During Er Tubule Formationmentioning

confidence: 99%

Myosin XI-Dependent Formation of Tubular Structures from Endoplasmic Reticulum Isolated from Tobacco Cultured BY-2 Cells

Yokota

Ueda²,

Hashimoto³

et al. 2011

Plant Physiology

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The reticular network of the endoplasmic reticulum (ER) consists of tubular and lamellar elements and is arranged in the cortical region of plant cells. This network constantly shows shape change and remodeling motion. Tubular ER structures were formed when GTP was added to the ER vesicles isolated from tobacco (Nicotiana tabacum) cultured BY-2 cells expressing ER-localized green fluorescent protein. The hydrolysis of GTP during ER tubule formation was higher than that under conditions in which ER tubule formation was not induced. Furthermore, a shearing force, such as the flow of liquid, was needed for the elongation/ extension of the ER tubule. The shearing force was assumed to correspond to the force generated by the actomyosin system in vivo. To confirm this hypothesis, the S12 fraction was prepared, which contained both cytosol and microsome fractions, including two classes of myosins, XI (175-kD myosin) and VIII (BY-2 myosin VIII-1), and ER-localized green fluorescent protein vesicles. The ER tubules and their mesh-like structures were arranged in the S12 fraction efficiently by the addition of ATP, GTP, and exogenous filamentous actin. The tubule formation was significantly inhibited by the depletion of 175-kD myosin from the S12 fraction but not BY-2 myosin VIII-1. Furthermore, a recombinant carboxyl-terminal tail region of 175-kD myosin also suppressed ER tubule formation. The tips of tubules moved along filamentous actin during tubule elongation. These results indicated that the motive force generated by the actomyosin system contributes to the formation of ER tubules, suggesting that myosin XI is responsible not only for the transport of ER in cytoplasm but also for the reticular organization of cortical ER.

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Section: Gtp Hydrolysis During Er Tubule Formationmentioning

confidence: 99%

Myosin XI-Dependent Formation of Tubular Structures from Endoplasmic Reticulum Isolated from Tobacco Cultured BY-2 Cells

Yokota

Ueda²,

Hashimoto³

et al. 2011

Plant Physiology

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“…The precise combination of Rab proteins and SNAREs determine the functional identity of numerous membrane compartments and guide fusion between donor and acceptor compartments (Pfeffer 2001;Murray et al 2002;Behnia and Munro 2005). Previous studies illustrate that the addition of recombinant Rab GDI reduces the efficiency of ER network formation in vitro, presumably by disrupting the membrane association of all Rab proteins (Turner et al 1997;Audhya et al 2007). Notably, no Rab protein has been identified that localizes specifically to the ER and affects ER fusion, morphology or dynamics; however, a Rab-interacting SNARE protein, yeast Ufe1, has previously been implicated in ER assembly and provides more evidence for the involvement of a Rab GTPase in ER assembly (Patel et al 1998;Anwar et al 2012).…”

Section: Er Dynamics and Assemblymentioning

confidence: 99%

“…In vitro systems for ER formation have suggested a role for Rab GTPases during ER vesicle fusion (Turner et al 1997;Audhya et al 2007). Rab proteins are GTP-binding proteins that control the fusion of target membranes through GTP hydrolysis (Cai et al 2007;Schwartz et al 2007).…”

Section: Er Dynamics and Assemblymentioning

confidence: 99%

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

English

Voeltz

2013

Cold Spring Harbor Perspectives in Biology

295

220

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The endoplasmic reticulum (ER) is a large, continuous membrane-bound organelle comprised of functionally and structurally distinct domains including the nuclear envelope, peripheral tubular ER, peripheral cisternae, and numerous membrane contact sites at the plasma membrane, mitochondria, Golgi, endosomes, and peroxisomes. These domains are required for multiple cellular processes, including synthesis of proteins and lipids, calcium level regulation, and exchange of macromolecules with various organelles at ER-membrane contact sites. The ER maintains its unique overall structure regardless of dynamics or transfer at ER-organelle contacts. In this review, we describe the numerous factors that contribute to the structure of the ER.T he endoplasmic reticulum (ER) is a dynamic organelle responsible for many cellular functions, including the synthesis of proteins and lipids, and regulation of intracellular calcium levels. This review focuses on the distinct and complex morphology of the ER. The structure of the ER is complex because of the numerous distinct domains that exist within one continuous membrane bilayer. These domains are shaped by interactions with the cytoskeleton, by proteins that stabilize membrane shape, and by a homotypic fusion machinery that allows the ER membrane to maintain its continuity and identity. The ER also contains domains that contact the plasma membrane (PM) and other organelles including the Golgi, endosomes, mitochondria, lipid droplets, and peroxisomes. ER contact sites with other organelles and the PM are both abundant and dispersed throughout the cytoplasm, suggesting that they too could influence the overall architecture of the ER. As we will discuss here, ER shape and distribution are regulated by many intrinsic and extrinsic forces. ER STRUCTURE AND FORMATION Domains of the ER Are Stabilized by Membrane-Shaping ProteinsThe endoplasmic reticulum (ER) is a large membrane-bound compartment spread throughout the cytoplasm of eukaryotic cells. It is divided into three major morphologies that include the nuclear envelope (NE), peripheral ER cisternae, and an interconnected tubular network

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“…This finding indicates the existence of other proteins implicated in the MAM domain establishment. Because Rab proteins regulate homotypic fusion of ER tubules (28), candidates for such proteins could be found among this extensive protein family. Members of these Rasrelated small GTPases direct intracellular vesicular traffic (29,30) but also regulate the structure of the ER and its apposition to other organelles.…”

mentioning

confidence: 99%

Rab32 Modulates Apoptosis Onset and Mitochondria-associated Membrane (MAM) Properties

Bui

Gilady

Fitzsimmons

et al. 2010

Journal of Biological Chemistry

150

146

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The mitochondria-associated membrane (MAM) has emerged as an endoplasmic reticulum (ER) signaling hub that accommodates ER chaperones, including the lectin calnexin. At the MAM, these chaperones control ER homeostasis but also play a role in the onset of ER stress-mediated apoptosis, likely through the modulation of ER calcium signaling. These opposing roles of MAM-localized chaperones suggest the existence of mechanisms that regulate the composition and the properties of ER membrane domains. Our results now show that the GTPase Rab32 localizes to the ER and mitochondria, and we identify this protein as a regulator of MAM properties. Consistent with such a role, Rab32 modulates ER calcium handling and disrupts the specific enrichment of calnexin on the MAM, while not affecting the ER distribution of protein-disulfide isomerase and mitofusin-2. Furthermore, Rab32 determines the targeting of PKA to mitochondrial and ER membranes and through its overexpression or inactivation increases the phosphorylation of Bad and of Drp1. Through a combination of its functions as a PKA-anchoring protein and a regulator of MAM properties, the activity and expression level of Rab32 determine the speed of apoptosis onset.

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A Rab GTPase Is Required for Homotypic Assembly of the Endoplasmic Reticulum

Cited by 29 publications

References 47 publications

Myosin XI-Dependent Formation of Tubular Structures from Endoplasmic Reticulum Isolated from Tobacco Cultured BY-2 Cells

Myosin XI-Dependent Formation of Tubular Structures from Endoplasmic Reticulum Isolated from Tobacco Cultured BY-2 Cells

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

Rab32 Modulates Apoptosis Onset and Mitochondria-associated Membrane (MAM) Properties

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