scholarly journals Amino acid and small GTPase regulation of mTORC1

2017 ◽  
Vol 7 (4) ◽  
pp. e1378794 ◽  
Author(s):  
Thu P. Nguyen ◽  
Anderson R. Frank ◽  
Jenna L. Jewell
Keyword(s):  
Amino Acid ◽  
Small Gtpase

The mammalian ARF-like protein 1 (Arl1) is associated with the Golgi complex

1996 ◽  
Vol 109 (1) ◽  
pp. 209-220 ◽  
Author(s):  
S.L. Lowe ◽  
S.H. Wong ◽  
W. Hong
Keyword(s):  
Amino Acid ◽  
Golgi Complex ◽  
Polyclonal Antibodies ◽  
Brefeldin A ◽  
Amino Acid Identity ◽  
Northern Blotting ◽  
Small Gtpase ◽  
Rat Tissues ◽  
Dependent Manner ◽  
Additional Cell

A rat cDNA clone was isolated which encodes a protein displaying characteristics of a ras-like small GTPase. The deduced amino acid sequence shows the highest amino acid identity (79%) with the Drosophila ARF-like protein 1 (dArl1) among all the known members of the ras-like small GTPase superfamily. The encoded protein was tentatively named rat Arl1 (rArl1). Northern blotting analysis revealed that the rArl1 gene is ubiquitously expressed in rat tissues. Recombinant rArl1 fused to glutathione-S-transferase (GST) to create GST-rArl1 binds GTP-gamma-S in a dose-dependent manner. Polyclonal antibodies raised against two unique rArl1 peptides recognized a 22 kDa protein in total NRK cell lysate. Immunofluorescence microscopy of NRK cells revealed discrete perinuclear labelling that could be competed out by GST-rArl1 but not GST. Examination of 8 additional cell lines revealed a similar labelling, suggesting that the antigen recognised by the antibodies is conserved and widely-expressed. Co-localization experiments in NRK cells with antibodies to mannosidase II and a newly identified cis-Golgi protein, p28, showed that rArl1 is localized to the Golgi complex. When cells were treated with nocodazole, the Golgi complex marked by mannosidase II and p28 was fragmented into punctate structures scattered throughout the cell, in which rArl1 was colocalized. Treatment with brefeldin A (BFA) resulted in the redistribution of rArl1 and mannosidase II into the cytoplasm and endoplasmic reticulum, respectively. The kinetics of the redistribution of rArl1 in response to BFA differ from those of ARF and beta-COP, two components of non-clathrin coated vesicles.

scholarly journals Unique COPII component AtSar1a/AtSec23a pair is required for the distinct function of protein ER export in Arabidopsis thaliana

2015 ◽  
Vol 112 (46) ◽  
pp. 14360-14365 ◽  
Author(s):  
Yonglun Zeng ◽  
Kin Pan Chung ◽  
Baiying Li ◽  
Ching Man Lai ◽  
Sheung Kwan Lam ◽  
...  
Keyword(s):  
Amino Acid ◽  
Functional Diversity ◽  
Specific Interaction ◽  
Cellular Level ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Single Amino Acid ◽  
Secretory Proteins ◽  
Amylase Secretion ◽  
Er Export

Secretory proteins traffic from endoplasmic reticulum (ER) to Golgi via the coat protein complex II (COPII) vesicle, which consists of five cytosolic components (Sar1, Sec23-24, and Sec13-31). In eukaryotes, COPII transport has diversified due to gene duplication, creating multiple COPII paralogs. Evidence has accumulated, revealing the functional heterogeneity of COPII paralogs in protein ER export. Sar1B, the small GTPase of COPII machinery, seems to be specialized for large cargo secretion in mammals. Arabidopsis contains five Sar1 and seven Sec23 homologs, and AtSar1a was previously shown to exhibit different effects on α-amylase secretion. However, mechanisms underlying the functional diversity of Sar1 paralogs remain unclear in higher organisms. Here, we show that the Arabidopsis Sar1 homolog AtSar1a exhibits distinct localization in plant cells. Transgenic Arabidopsis plants expressing dominant-negative AtSar1a exhibit distinct effects on ER cargo export. Mutagenesis analysis identified a single amino acid, Cys84, as being responsible for the functional diversity of AtSar1a. Structure homology modeling and interaction studies revealed that Cys84 is crucial for the specific interaction of AtSar1a with AtSec23a, a distinct Arabidopsis Sec23 homolog. Structure modeling and coimmunoprecipitation further identified a corresponding amino acid, Cys484, on AtSec23a as being essential for the specific pair formation. At the cellular level, the Cys484 mutation affects the distinct function of AtSec23a on vacuolar cargo trafficking. Additionally, dominant-negative AtSar1a affects the ER export of the transcription factor bZIP28 under ER stress. We have demonstrated a unique plant pair of COPII machinery function in ER export and the mechanism underlying the functional diversity of COPII paralogs in eukaryotes.

scholarly journals Control of TSC2-Rheb signaling axis by arginine regulates mTORC1 activity

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Bernadette Carroll ◽  
Dorothea Maetzel ◽  
Oliver DK Maddocks ◽  
Gisela Otten ◽  
Matthew Ratcliff ◽  
...  
Keyword(s):  
Amino Acid ◽  
Mammalian Target Of Rapamycin ◽  
Embryonic Stem ◽  
Cell Types ◽  
Cellular Protein ◽  
Small Gtpase ◽  
Growth Factor Signaling ◽  
Mtorc1 Signaling ◽  
Signaling Axis ◽  
Intracellular Amino Acids

The mammalian target of rapamycin complex 1 (mTORC1) is the key signaling hub that regulates cellular protein homeostasis, growth, and proliferation in health and disease. As a prerequisite for activation of mTORC1 by hormones and mitogens, there first has to be an available pool of intracellular amino acids. Arginine, an amino acid essential during mammalian embryogenesis and early development is one of the key activators of mTORC1. Herein, we demonstrate that arginine acts independently of its metabolism to allow maximal activation of mTORC1 by growth factors via a mechanism that does not involve regulation of mTORC1 localization to lysosomes. Instead, arginine specifically suppresses lysosomal localization of the TSC complex and interaction with its target small GTPase protein, Rheb. By interfering with TSC-Rheb complex, arginine relieves allosteric inhibition of Rheb by TSC. Arginine cooperates with growth factor signaling which further promotes dissociation of TSC2 from lysosomes and activation of mTORC1. Arginine is the main amino acid sensed by the mTORC1 pathway in several cell types including human embryonic stem cells (hESCs). Dependence on arginine is maintained once hESCs are differentiated to fibroblasts, neurons, and hepatocytes, highlighting the fundamental importance of arginine-sensing to mTORC1 signaling. Together, our data provide evidence that different growth promoting cues cooperate to a greater extent than previously recognized to achieve tight spatial and temporal regulation of mTORC1 signaling.

scholarly journals A Ragulator–BORC interaction controls lysosome positioning in response to amino acid availability

2017 ◽  
Vol 216 (12) ◽  
pp. 4183-4197 ◽  
Author(s):  
Jing Pu ◽  
Tal Keren-Kaplan ◽  
Juan S. Bonifacino
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cellular Response ◽  
Mammalian Target Of Rapamycin ◽  
Small Gtpase ◽  
Regulatory Effect ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Amino Acid Availability ◽  
Amino Acid Depletion

Lysosomes play key roles in the cellular response to amino acid availability. Depletion of amino acids from the medium turns off a signaling pathway involving the Ragulator complex and the Rag guanosine triphosphatases (GTPases), causing release of the inactive mammalian target of rapamycin complex 1 (mTORC1) serine/threonine kinase from the lysosomal membrane. Decreased phosphorylation of mTORC1 substrates inhibits protein synthesis while activating autophagy. Amino acid depletion also causes clustering of lysosomes in the juxtanuclear area of the cell, but the mechanisms responsible for this phenomenon are poorly understood. Herein we show that Ragulator directly interacts with BLOC-1–related complex (BORC), a multi-subunit complex previously found to promote lysosome dispersal through coupling to the small GTPase Arl8 and the kinesins KIF1B and KIF5B. Interaction with Ragulator exerts a negative regulatory effect on BORC that is independent of mTORC1 activity. Amino acid depletion strengthens this interaction, explaining the redistribution of lysosomes to the juxtanuclear area. These findings thus demonstrate that amino acid availability controls lysosome positioning through Ragulator-dependent, but mTORC1-independent, modulation of BORC.

The staining pattern of the tropomyosin sequence is displayed in a new paracrystal

1986 ◽  
Vol 44 ◽  
pp. 150-151
Author(s):  
M.K. Lamvik ◽  
L.L. Klatt
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Staining Pattern ◽  
Banding Patterns ◽  
Mass Thickness ◽  
New Form

Tropomyosin paracrystals have been used extensively as test specimens and magnification standards due to their clear periodic banding patterns. The paracrystal type discovered by Ohtsuki1 has been of particular interest as a test of unstained specimens because of alternating bands that differ by 50% in mass thickness. While producing specimens of this type, we came across a new paracrystal form. Since this new form displays aligned tropomyosin molecules without the overlaps that are characteristic of the Ohtsuki-type paracrystal, it presents a staining pattern that corresponds to the amino acid sequence of the molecule.

Electron probe x-ray microanalysis and electron microscopy of amino acid absorption and transport by the small intestine: inhibition by chemical poisons and correlation to the elemental composition of the epithelial cells

1986 ◽  
Vol 44 ◽  
pp. 134-135
Author(s):  
A. J. Tousimis
Keyword(s):  
Small Intestine ◽  
Amino Acid ◽  
Epithelial Cells ◽  
Elemental Composition ◽  
Isotope Labeling ◽  
Structural Components ◽  
X Ray ◽  
Human Small Intestine ◽  
Transport Studies

The elemental composition of amino acids is similar to that of the major structural components of the epithelial cells of the small intestine and other tissues. Therefore, their subcellular localization and concentration measurements are not possible by x-ray microanalysis. Radioactive isotope labeling: I131-tyrosine, Se75-methionine and S35-methionine have been successfully employed in numerous absorption and transport studies. The latter two have been utilized both in vitro and vivo, with similar results in the hamster and human small intestine. Non-radioactive Selenomethionine, since its absorption/transport behavior is assumed to be the same as that of Se75- methionine and S75-methionine could serve as a compound tracer for this amino acid.

Immunoelectron microscope detection of C-type natriuretic peptide in normal human atrial tissue

1993 ◽  
Vol 51 ◽  
pp. 388-389
Author(s):  
Chi-Ming Wei ◽  
Margaret Hukee ◽  
Christopher G.A. McGregor ◽  
John C. Burnett
Keyword(s):  
Amino Acid ◽  
Natriuretic Peptide ◽  
Vascular Tone ◽  
Cardiac Tissue ◽  
Ring Structure ◽  
Terminal Amino Acid ◽  
Amino Acid Peptide ◽  
Normal Human ◽  
Terminal Amino ◽  
The Brain

C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial (ANP) and brain natriuretic peptide (BNP). CNP exists as a 22-amino acid peptide and like ANP and BNP has a 17-amino acid ring formed by a disulfide bond. Unlike these two previously identified cardiac peptides, CNP lacks the COOH-terminal amino acid extension from the ring structure. ANP, BNP and CNP decrease cardiac preload, but unlike ANP and BNP, CNP is not natriuretic. While ANP and BNP have been localized to the heart, recent investigations have failed to detect CNP mRNA in the myocardium although small concentrations of CNP are detectable in the porcine myocardium. While originally localized to the brain, recent investigations have localized CNP to endothelial cells consistent with a paracrine role for CNP in the control of vascular tone. While CNP has been detected in cardiac tissue by radioimmunoassay, no studies have demonstrated CNP localization in normal human heart by immunoelectron microscopy.

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