scholarly journals Subunit exchange among endolysosomal tethering complexes is linked to contact site formation at the vacuole

2021 ◽  
Author(s):  
Ayelén González Montoro ◽  
Prado Vargas Duarte ◽  
Kathrin Auffarth ◽  
Stefan Walter ◽  
Florian Fröhlich ◽  
...  
Keyword(s):  
Protein Sorting ◽  
Specific Role ◽  
Site Formation ◽  
Contact Site ◽  
Subunit Exchange ◽  
Hybrid Complex ◽  
Membrane Contact ◽  
And Function ◽  
Shed Light

The hexameric HOPS (homotypic fusion and protein sorting) complex is a conserved tethering complex at the lysosome-like vacuole, where it mediates tethering and promotes all fusion events involving this organelle. The Vps39 subunit of this complex also engages in a membrane contact site between the vacuole and the mitochondria, called vCLAMP. Additionally, four subunits of HOPS are also part of the endosomal CORVET tethering complex. Here, we analyzed the partition of HOPS and CORVET subunits between the different complexes by tracing their localization and function. We find that Vps39 has a specific role in vCLAMP formation beyond tethering, and that vCLAMPs and HOPS compete for the same pool of Vps39. In agreement, we find that the CORVET subunit Vps3 can take the position of Vps39 in HOPS. This endogenous pool of a Vps3-hybrid complex is affected by Vps3 or Vps39 levels, suggesting that HOPS and CORVET assembly is dynamic. Our data shed light on how individual subunits of tethering complexes such as Vps39 can participate in other functions, while maintaining the remaining subcomplex available for its function in tethering and fusion.

scholarly journals Lysosomal Biology and Function: Modern View of Cellular Debris Bin

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1131 ◽  
Author(s):  
Purvi C. Trivedi ◽  
Jordan J. Bartlett ◽  
Thomas Pulinilkunnil
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Current Knowledge ◽  
Site Formation ◽  
Cellular Debris ◽  
Vesicular Membrane ◽  
Nutrient Signaling ◽  
Membrane Contact ◽  
And Function ◽  
Chaperone Mediated Autophagy

Lysosomes are the main proteolytic compartments of mammalian cells comprising of a battery of hydrolases. Lysosomes dispose and recycle extracellular or intracellular macromolecules by fusing with endosomes or autophagosomes through specific waste clearance processes such as chaperone-mediated autophagy or microautophagy. The proteolytic end product is transported out of lysosomes via transporters or vesicular membrane trafficking. Recent studies have demonstrated lysosomes as a signaling node which sense, adapt and respond to changes in substrate metabolism to maintain cellular function. Lysosomal dysfunction not only influence pathways mediating membrane trafficking that culminate in the lysosome but also govern metabolic and signaling processes regulating protein sorting and targeting. In this review, we describe the current knowledge of lysosome in influencing sorting and nutrient signaling. We further present a mechanistic overview of intra-lysosomal processes, along with extra-lysosomal processes, governing lysosomal fusion and fission, exocytosis, positioning and membrane contact site formation. This review compiles existing knowledge in the field of lysosomal biology by describing various lysosomal events necessary to maintain cellular homeostasis facilitating development of therapies maintaining lysosomal function.

scholarly journals Serine palmitoyltransferase assembles at ER–mitochondria contact sites

2021 ◽  
Vol 5 (2) ◽  
pp. e202101278
Author(s):  
Mari J Aaltonen ◽  
Irina Alecu ◽  
Tim König ◽  
Steffany AL Bennett ◽  
Eric A Shoubridge
Keyword(s):  
De Novo ◽  
Outer Mitochondrial Membrane ◽  
Serine Palmitoyltransferase ◽  
Contact Site ◽  
Contact Sites ◽  
A Subunit ◽  
In Trans ◽  
Membrane Contact ◽  
And Function ◽  
Insight Into

The accumulation of sphingolipid species in the cell contributes to the development of obesity and neurological disease. However, the subcellular localization of sphingolipid-synthesizing enzymes is unclear, limiting the understanding of where and how these lipids accumulate inside the cell and why they are toxic. Here, we show that SPTLC2, a subunit of the serine palmitoyltransferase (SPT) complex, catalyzing the first step in de novo sphingolipid synthesis, localizes dually to the ER and the outer mitochondrial membrane. We demonstrate that mitochondrial SPTLC2 interacts and forms a complex in trans with the ER-localized SPT subunit SPTLC1. Loss of SPTLC2 prevents the synthesis of mitochondrial sphingolipids and protects from palmitate-induced mitochondrial toxicity, a process dependent on mitochondrial ceramides. Our results reveal the in trans assembly of an enzymatic complex at an organellar membrane contact site, providing novel insight into the localization of sphingolipid synthesis and the composition and function of ER–mitochondria contact sites.

scholarly journals The ER Stress Sensor PERK Coordinates ER-Plasma Membrane Contact Site Formation through Interaction with Filamin-A and F-Actin Remodeling

2017 ◽  
Vol 65 (5) ◽  
pp. 885-899.e6 ◽  
Author(s):  
Alexander R. van Vliet ◽  
Francesca Giordano ◽  
Sarah Gerlo ◽  
Inmaculada Segura ◽  
Sofie Van Eygen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Er Stress ◽  
Site Formation ◽  
Filamin A ◽  
Contact Site ◽  
Actin Remodeling ◽  
Stress Sensor ◽  
Membrane Contact

scholarly journals Messianism, rationalism and inter-Asian connections: The Majalis-i Jahangiri (1608–11) and the socio-intellectual history of the Mughal ‘ulama

2017 ◽  
Vol 54 (3) ◽  
pp. 317-338 ◽  
Author(s):  
Corinne Lefèvre
Keyword(s):  
Central Asia ◽  
Intellectual History ◽  
State Building ◽  
Specific Role ◽  
Wide Range ◽  
History Of ◽  
Muslim Intellectuals ◽  
Shed Light

Relying on the Majalis-i Jahangiri (1608–11) by ʿAbd al-Sattar b. Qasim Lahauri, this essay explores some of the discussions the Mughal Emperor Jahangir (r. 1605–27) conducted with a wide range of scholars, from Brahmans and ʿulama to Jesuit padres and Jewish savants. By far the most numerous, the debates bearing on Islam and involving Muslim intellectuals are especially significant on several accounts. First, because they illuminate how, following in the steps of his father Akbar (r. 1556–605), Jahangir was able to conciliate his messianic claims with a strong engagement with reason and to turn this combination into a formidable instrument for confession and state building. These conversations also provide promising avenues to think afresh the socio-intellectual history of the Mughal ʿulama inasmuch as they capture the challenges and adjustments attendant on imperial patronage, depict the jockeying for influence and positions among intellectuals (particularly between Indo-Muslim and Iranian lettrés), and shed light on relatively little known figures or on unexplored facets of more prominent individuals. In addition, the specific role played by scholars hailing from Iran—and, to a lesser extent, from Central Asia—in the juridical-religious disputes of the Indian court shows how crucial inter-Asian connections and networks were in the fashioning of Mughal ideology but also the ways in which the ongoing flow of émigré ʿulama was disciplined before being incorporated into the empire.

scholarly journals Emerging strategies to target RAS signaling in human cancer therapy

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Kun Chen ◽  
Yalei Zhang ◽  
Ling Qian ◽  
Peng Wang
Keyword(s):  
Human Cancer ◽  
Ras Signaling ◽  
Targeting Therapy ◽  
Ras Protein ◽  
Patients With Cancer ◽  
Mutational Status ◽  
Poor Differentiation ◽  
And Function ◽  
Nsclc Patients ◽  
Shed Light

AbstractRAS mutations (HRAS, NRAS, and KRAS) are among the most common oncogenes, and around 19% of patients with cancer harbor RAS mutations. Cells harboring RAS mutations tend to undergo malignant transformation and exhibit malignant phenotypes. The mutational status of RAS correlates with the clinicopathological features of patients, such as mucinous type and poor differentiation, as well as response to anti-EGFR therapies in certain types of human cancers. Although RAS protein had been considered as a potential target for tumors with RAS mutations, it was once referred to as a undruggable target due to the consecutive failure in the discovery of RAS protein inhibitors. However, recent studies on the structure, signaling, and function of RAS have shed light on the development of RAS-targeting drugs, especially with the approval of Lumakras (sotorasib, AMG510) in treatment of KRASG12C-mutant NSCLC patients. Therefore, here we fully review RAS mutations in human cancer and especially focus on emerging strategies that have been recently developed for RAS-targeting therapy.

P53/miR-34a/SIRT1 Positive Feedback Loop regulates cell proliferation and promotes cell apoptosis in the termination stage of liver regeneration.

2021 ◽  
Author(s):  
Junhua Gong ◽  
Minghua Cong ◽  
Hao Wu ◽  
Menghao Wang ◽  
He Bai ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Liver Regeneration ◽  
Positive Feedback ◽  
Cell Apoptosis ◽  
Feedback Loop ◽  
Late Phase ◽  
Liver Weight ◽  
Positive Feedback Loop ◽  
And Function ◽  
Shed Light

Abstract Background The capacity of the liver to restore its architecture and function assures good prognoses of patients who suffer serious hepatic injury or cancer resection. In our study, we found that the P53/miR-34a/SIRT1 positive feedback loop has a remarkable negative regulatory effect, which is related to the termination of liver regeneration. Here, we described how P53/miR-34a/SIRT1 positive feedback loop controls liver regeneration and its possible relationship with liver cancer.Method We performed partial hepatectomy (PH) in mice transfected with adenovirus (Ade) overexpressing P53 and adenovirus-associated virus (AAV) knock-downing miR-34a. LR was analyzed by liver weight/body weight, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and cell proliferation, and the related cellular signals were investigated. Bile acid (BA) levels during LR were analyzed by metabolomics of bile acids. Results We found that the P53/miR-34a/SIRT1 positive feedback loop was activated in the late phase of LR. Overexpression of P53 terminated LR early and enhanced P53/miR-34a/SIRT1 positive feedback loop expression and its proapoptotic effect. Mice from the Ade-P53 group showed smaller livers and higher levels of serum ALT and AST than control mice. While knock-down of miR-34a abolished P53/miR-34a/SIRT1 positive feedback loop during LR. Mice from anti-miR-34a group showed larger livers and lower levels of PCNA-positive cells than control mice. T-β-MCA increased gradually during LR and peaked at 7 days after PH. T-β-MCA inhibited cell proliferation and promoted cell apoptosis via facilitating the P53/miR-34a/SIRT1 positive feedback loop during LR by suppressing FXR/SHP. Conclusion The P53/miR-34a/SIRT1 positive feedback loop plays an important role in the termination of LR. Our findings shed light on the molecular and metabolic mechanisms of LR termination and provide a potential therapeutic alternative for treating P53-wild-type HCC patients.

Targeted deletion of the ATP binding domain of left-right dynein confirms its role in specifying development of left-right asymmetries

Development ◽  
1999 ◽  
Vol 126 (23) ◽  
pp. 5495-5504 ◽  
Author(s):  
D.M. Supp ◽  
M. Brueckner ◽  
M.R. Kuehn ◽  
D.P. Witte ◽  
L.A. Lowe ◽  
...  
Keyword(s):  
Motor Function ◽  
Single Amino Acid ◽  
Atp Binding ◽  
Amino Acid Difference ◽  
Sequence Classification ◽  
Ciliated Cells ◽  
Targeted Deletion ◽  
Targeted Mutation ◽  
And Function ◽  
Shed Light

Vertebrates develop distinct asymmetries along the left-right axis, which are consistently aligned with the anteroposterior and dorsoventral axes. The mechanisms that direct this handed development of left-right asymmetries have been elusive, but recent studies of mutations that affect left-right development have shed light on the molecules involved. One molecule implicated in left-right specification is left-right dynein (LRD), a microtubule-based motor protein. In the LRD protein of the inversus viscerum (iv) mouse, there is a single amino acid difference at a conserved position, and the lrd gene is one of many genes deleted in the legless (lgl) mutation. Both iv and lgl mice display randomized left-right development. Here we extend the analysis of the lrd gene at the levels of sequence, expression and function. The complete coding sequence of the lrd gene confirms its classification as an axonemal, or ciliary, dynein. Expression of lrd in the node at embryonic day 7.5 is shown to be symmetric. At embryonic day 8.0, however, a striking asymmetric expression pattern is observed in all three germ layers of the developing headfold, suggesting roles in both the establishment and maintenance of left-right asymmetries. At later times, expression of lrd is also observed in the developing floorplate, gut and limbs. These results suggest function for LRD protein in both ciliated and non-ciliated cells, despite its sequence classification as axonemal. In addition, a targeted mutation of lrd was generated that deletes the part of the protein required for ATP binding, and hence motor function. The resulting left-right phenotype, randomization of laterality, is identical to that of iv and lgl mutants. Gross defects in ciliary structure were not observed in lrd/lrd mutants. Strikingly, however, the monocilia on mutant embryonic node cells were immotile. These results prove the identity of the iv and lrd genes. Further, they argue that LRD motor function, and resulting nodal monocilia movement, are required for normal left-right development.

scholarly journals An Interorganellar Bidding War: Vps13 Localization by Competitive Organelle-Specific Adaptors

Contact ◽  
2018 ◽  
Vol 1 ◽  
pp. 251525641881462
Author(s):  
Samantha K. Dziurdzik ◽  
Björn D.M. Bean ◽  
Elizabeth Conibear
Keyword(s):  
Endoplasmic Reticulum ◽  
Recent Work ◽  
Protein Sorting ◽  
Repeat Region ◽  
Vacuolar Protein Sorting ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Prospore Membrane ◽  
Membrane Contact ◽  
Vacuolar Protein

Membrane contact sites are regulated through the controlled recruitment of constituent proteins. Yeast vacuolar protein sorting 13 (Vps13) dynamically localizes to membrane contact sites at endosomes, vacuoles, mitochondria, and the endoplasmic reticulum under different cellular conditions and is recruited to the prospore membrane during meiosis. Prior to our recent work, the mechanism for localization at contact sites was largely unknown. We identified Ypt35 as a novel Vps13 adaptor for endosomes and the nucleus-vacuole junction. Furthermore, we discovered a conserved recruitment motif in Ypt35 and found related motifs in the prospore membrane and mitochondrial adaptors, Spo71 and Mcp1, respectively. All three adaptors compete for binding to a six-repeat region of Vps13, suggesting adaptor competition regulates Vps13 localization. Here, we summarize and discuss the implications of our work, highlighting key outstanding questions.

scholarly journals Reverse evolution leads to genotypic incompatibility despite functional and active site convergence

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Miriam Kaltenbach ◽  
Colin J Jackson ◽  
Eleanor C Campbell ◽  
Florian Hollfelder ◽  
Nobuhiko Tokuriki
Keyword(s):  
Active Site ◽  
Adaptive Landscape ◽  
Sequence Structure ◽  
Activity Increase ◽  
Enzyme Active Site ◽  
Fundamental Relationship ◽  
And Function ◽  
Alternative Set ◽  
Shed Light ◽  
New Mutations

Understanding the extent to which enzyme evolution is reversible can shed light on the fundamental relationship between protein sequence, structure, and function. Here, we perform an experimental test of evolutionary reversibility using directed evolution from a phosphotriesterase to an arylesterase, and back, and examine the underlying molecular basis. We find that wild-type phosphotriesterase function could be restored (>104-fold activity increase), but via an alternative set of mutations. The enzyme active site converged towards its original state, indicating evolutionary constraints imposed by catalytic requirements. We reveal that extensive epistasis prevents reversions and necessitates fixation of new mutations, leading to a functionally identical sequence. Many amino acid exchanges between the new and original enzyme are not tolerated, implying sequence incompatibility. Therefore, the evolution was phenotypically reversible but genotypically irreversible. Our study illustrates that the enzyme's adaptive landscape is highly rugged, and different functional sequences may constitute separate fitness peaks.

scholarly journals Unexpected cryptic species among streptophyte algae most distant to land plants

2021 ◽  
Vol 288 (1963) ◽  
Author(s):  
Iker Irisarri ◽  
Tatyana Darienko ◽  
Thomas Pröschold ◽  
Janine M. R. Fürst-Jansen ◽  
Mahwash Jamy ◽  
...  
Keyword(s):  
Land Plants ◽  
Comparative Genomic ◽  
Future Studies ◽  
Form And Function ◽  
Genomic Studies ◽  
Plant Form ◽  
Phylogenomic Analyses ◽  
And Function ◽  
Shed Light ◽  
Green Lineage

Streptophytes are one of the major groups of the green lineage (Chloroplastida or Viridiplantae). During one billion years of evolution, streptophytes have radiated into an astounding diversity of uni- and multicellular green algae as well as land plants. Most divergent from land plants is a clade formed by Mesostigmatophyceae, Spirotaenia spp. and Chlorokybophyceae. All three lineages are species-poor and the Chlorokybophyceae consist of a single described species, Chlorokybus atmophyticus. In this study, we used phylogenomic analyses to shed light into the diversity within Chlorokybus using a sampling of isolates across its known distribution. We uncovered a consistent deep genetic structure within the Chlorokybus isolates, which prompted us to formally extend the Chlorokybophyceae by describing four new species. Gene expression differences among Chlorokybus species suggest certain constitutive variability that might influence their response to environmental factors. Failure to account for this diversity can hamper comparative genomic studies aiming to understand the evolution of stress response across streptophytes. Our data highlight that future studies on the evolution of plant form and function can tap into an unknown diversity at key deep branches of the streptophytes.

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