scholarly journals Bipartite binding and partial inhibition links DEPTOR and mTOR in a mutually antagonistic embrace

2021 ◽  
Author(s):  
Roger L Williams ◽  
Maren Heimhalt ◽  
Alex Berndt ◽  
Jane L Wagstaff ◽  
Madhanagopal Anandapadamanaban ◽  
...  
Keyword(s):  
Cell Growth ◽  
Feedback Inhibition ◽  
Pdz Domain ◽  
Partial Inhibition ◽  
Oncogenic Mutation ◽  
Mutual Antagonism ◽  
Exogenous Factors

mTORC1 is a kinase complex regulating cell growth, proliferation and survival. Because mis-regulation of DEPTOR, an endogenous mTORC1 inhibitor, is associated with some cancers, we reconstituted mTORC1 with DEPTOR to understand its function. We find that DEPTOR is a unique partial mTORC1 inhibitor that may have evolved to preserve feedback inhibition of PI3K. Counterintuitively, mTORC1 activated by RHEB or oncogenic mutation is much more potently inhibited by DEPTOR. Although DEPTOR partially inhibits mTORC1, mTORC1 prevents this inhibition by phosphorylating DEPTOR, a mutual antagonism that requires no exogenous factors. Structural analyses of the mTORC1/DEPTOR complex showed DEPTOR's PDZ domain interacting with the mTOR FAT region, and the unstructured linker preceding the PDZ binding to the mTOR FRB domain. Here we show, in contrast to previous cellular studies, that both the PDZ and linker regions are essential for inhibition, and it is likely that interaction with the FRB is crucial to the unique partial inhibition.

scholarly journals Bipartite binding and partial inhibition links DEPTOR and mTOR in a mutually antagonistic embrace

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Maren Heimhalt ◽  
Alex Berndt ◽  
Jane Wagstaff ◽  
Madhanagopal Anandapadamanaban ◽  
Olga Perisic ◽  
...  
Keyword(s):  
Cell Growth ◽  
Feedback Inhibition ◽  
Pdz Domain ◽  
Partial Inhibition ◽  
Oncogenic Mutation ◽  
Mutual Antagonism ◽  
Exogenous Factors

The mTORC1 kinase complex regulates cell growth, proliferation, and survival. Because mis-regulation of DEPTOR, an endogenous mTORC1 inhibitor, is associated with some cancers, we reconstituted mTORC1 with DEPTOR to understand its function. We find that DEPTOR is a unique partial mTORC1 inhibitor that may have evolved to preserve feedback inhibition of PI3K. Counterintuitively, mTORC1 activated by RHEB or oncogenic mutation is much more potently inhibited by DEPTOR. Although DEPTOR partially inhibits mTORC1, mTORC1 prevents this inhibition by phosphorylating DEPTOR, a mutual antagonism that requires no exogenous factors. Structural analyses of the mTORC1/DEPTOR complex showed DEPTOR’s PDZ domain interacting with the mTOR FAT region, and the unstructured linker preceding the PDZ binding to the mTOR FRB domain. The linker and PDZ form the minimal inhibitory unit, but the N-terminal tandem DEP domains also significantly contribute to inhibition.

scholarly journals Antizyme induction by polyamine analogues as a factor of cell growth inhibition

2002 ◽  
Vol 366 (2) ◽  
pp. 663-671 ◽  
Author(s):  
John L.A. MITCHELL ◽  
Aviva LEYSER ◽  
Michelle S. HOLTORFF ◽  
Jill S. BATES ◽  
Benjamin FRYDMAN ◽  
...  
Keyword(s):  
Cell Growth ◽  
Growth Inhibition ◽  
Feedback Inhibition ◽  
Conformationally Constrained ◽  
Polyamine Analogues ◽  
Polyamine Transport ◽  
Mammalian Cell Growth ◽  
Htc Cells ◽  
Cell Growth And Viability ◽  
Selection Of

The polyamines spermidine and spermine and their diamine precursor putrescine are essential for mammalian cell growth and viability, and strategies are sought for reducing polyamine levels in order to inhibit cancer growth. Several structural analogues of the polyamines have been found to decrease natural polyamine levels and inhibit cell growth, probably by stimulating normal feedback mechanisms. In the present study, a large selection of spermine analogues has been tested for their effectiveness in inducing the production of antizyme, a key protein in feedback inhibition of putrescine synthesis and cellular polyamine uptake. Bisethylnorspermine, bisethylhomospermine, 1,19-bis-(ethylamino)-5,10,15-triazanonadecane, longer oligoamine constructs and many conformationally constrained analogues of these compounds were found to stimulate antizyme synthesis to different levels in rat liver HTC cells, with some producing far more antizyme than the natural polyamine spermine. Uptake of the tested compounds was found to be dependent on, and limited by, the polyamine transport system, for which all these have approximately equal affinity. These analogues differed in their ability to inhibit HTC cell growth during 3days of exposure, and this ability correlated with their antizyme-inducing potential. This is the first direct evidence that antizyme is induced by several polyamine analogues. Selection of analogues with this potential may be an effective strategy for maximizing polyamine deprivation and growth inhibition.

scholarly journals VIP interneurons in mouse primary visual cortex selectively enhance responses to weak but specific stimuli

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Daniel J Millman ◽  
Gabriel Koch Ocker ◽  
Shiella Caldejon ◽  
India Kato ◽  
Josh D Larkin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Pyramidal Neurons ◽  
Feedback Inhibition ◽  
Neuron Activity ◽  
Low Contrast ◽  
Visual Coding ◽  
Mutual Antagonism ◽  
Layer 2 ◽  
Highly Correlated

Vasoactive intestinal peptide-expressing (VIP) interneurons in the cortex regulate feedback inhibition of pyramidal neurons through suppression of somatostatin-expressing (SST) interneurons and, reciprocally, SST neurons inhibit VIP neurons. Although VIP neuron activity in the primary visual cortex (V1) of mouse is highly correlated with locomotion, the relevance of locomotion-related VIP neuron activity to visual coding is not known. Here we show that VIP neurons in mouse V1 respond strongly to low contrast front-to-back motion that is congruent with self-motion during locomotion but are suppressed by other directions and contrasts. VIP and SST neurons have complementary contrast tuning. Layer 2/3 contains a substantially larger population of low contrast preferring pyramidal neurons than deeper layers, and layer 2/3 (but not deeper layer) pyramidal neurons show bias for front-to-back motion specifically at low contrast. Network modeling indicates that VIP-SST mutual antagonism regulates the gain of the cortex to achieve sensitivity to specific weak stimuli without compromising network stability.

scholarly journals Feedback Inhibition of Amidophosphoribosyltransferase Regulates the Rate of Cell Growth via Purine Nucleotide, DNA, and Protein Syntheses

2001 ◽  
Vol 276 (24) ◽  
pp. 21285-21291 ◽  
Author(s):  
Takashi Yamaoka ◽  
Makiko Yano ◽  
Maki Kondo ◽  
Hidemi Sasaki ◽  
Satoshi Hino ◽  
...  
Keyword(s):  
Cell Growth ◽  
Feedback Inhibition ◽  
Purine Nucleotide

scholarly journals Antizyme inhibitor is rapidly induced in growth-stimulated mouse fibroblasts and releases ornithine decarboxylase from antizyme suppression

2000 ◽  
Vol 346 (3) ◽  
pp. 699-704 ◽  
Author(s):  
Jonas NILSSON ◽  
Birgitta GRAHN ◽  
Olle HEBY
Keyword(s):  
Cell Growth ◽  
Ornithine Decarboxylase ◽  
Feedback Inhibition ◽  
Growth Stimulation ◽  
Culture Conditions ◽  
Mouse Fibroblasts ◽  
Antizyme Inhibitor ◽  
Plasmid Construct ◽  
Mrna Content

Ornithine decarboxylase (ODC) catalyses the first step in the synthesis of the polyamines putrescine, spermidine and spermine. The polyamines are essential for cell growth, but at elevated levels they may be tumorigenic, toxic, or may induce apoptosis. Therefore, ODC activity is highly regulated. It is induced when cells are stimulated to grow, and it is subjected to feedback inhibition by the polyamines. By causing ribosomal frameshifting, polyamines induce the synthesis of antizyme, a 23-kDa protein, which binds to ODC, inhibits its activity and promotes its degradation by the 26 S proteasome. Antizyme, in turn, is inhibited by antizyme inhibitor (AZI). We describe the cloning of a mouse AZI cDNA, encoding a protein with high homology to mouse ODC. Using purified recombinant proteins, we show that AZI (which has no ODC activity) can release enzymically active ODC from antizyme suppression in vitro. We also show that ODC reactivation takes place in mouse fibroblasts upon transient transfection with an AZI-expressing plasmid construct. Finally we demonstrate that the AZI mRNA content of mouse fibroblasts increases significantly within an hour of growth stimulation, i.e. much earlier than ODC transcripts. Our results indicate that induction of AZI synthesis may represent a means of rescuing ODC molecules that have been inactivated and tagged for degradation by antizyme, when culture conditions improve and polyamine production is needed for cell growth and proliferation.

scholarly journals Regulation of human mTOR complexes by DEPTOR

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Matthias Wälchli ◽  
Karolin Berneiser ◽  
Francesca Mangia ◽  
Stefan Imseng ◽  
Louise-Marie Craigie ◽  
...  
Keyword(s):  
Cell Growth ◽  
Tumor Suppressor ◽  
Signaling Pathways ◽  
Biochemical Analysis ◽  
Pdz Domain ◽  
Mammalian Target Of Rapamycin ◽  
Interacting Protein ◽  
Mtor Complex 1 ◽  
Binding Interfaces ◽  
Mtor Activity

The vertebrate-specific DEP domain-containing mTOR interacting protein (DEPTOR), an oncoprotein or tumor suppressor, has important roles in metabolism, immunity, and cancer. It is the only protein that binds and regulates both complexes of mammalian target of rapamycin (mTOR), a central regulator of cell growth. Biochemical analysis and cryo-EM reconstructions of DEPTOR bound to human mTOR complex 1 (mTORC1) and mTORC2 reveal that both structured regions of DEPTOR, the PDZ domain and the DEP domain tandem (DEPt), are involved in mTOR interaction. The PDZ domain binds tightly with mildly activating effect, but then acts as an anchor for DEPt association that allosterically suppresses mTOR activation. The binding interfaces of the PDZ domain and DEPt also support further regulation by other signaling pathways. A separate, substrate-like mode of interaction for DEPTOR phosphorylation by mTOR complexes rationalizes inhibition of non-stimulated mTOR activity at higher DEPTOR concentrations. The multifaceted interplay between DEPTOR and mTOR provides a basis for understanding the divergent roles of DEPTOR in physiology and opens new routes for targeting the mTOR-DEPTOR interaction in disease.

scholarly journals VIP interneurons selectively enhance weak but behaviorally-relevant stimuli

2019 ◽  
Author(s):  
Daniel J. Millman ◽  
Gabriel Koch Ocker ◽  
Shiella Caldejon ◽  
India Kato ◽  
Josh D. Larkin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Vasoactive Intestinal Peptide ◽  
Primary Visual Cortex ◽  
Visual Motion ◽  
Pyramidal Neurons ◽  
Feedback Inhibition ◽  
Network Modeling ◽  
Network Stability ◽  
Mutual Antagonism

AbstractVasoactive intestinal peptide-expressing (VIP) interneurons in cortex regulate feedback inhibition of pyramidal neurons through suppression of somatostatin-expressing (SST) interneurons and, reciprocally, SST neurons inhibit VIP neurons. Here, we show that VIP neurons in mouse primary visual cortex have complementary contrast tuning to SST neurons and respond synergistically to front-to-back visual motion and locomotion. Network modeling indicates that this VIP-SST mutual antagonism regulates the gain of cortex to achieve both sensitivity to behaviorally-relevant stimuli and network stability.

Electron Microscopic Study of the Epithelium of the Seminal Vesicle of Aging Rats

1974 ◽  
Vol 32 ◽  
pp. 138-139
Author(s):  
V. F. Allison ◽  
G. C. Fink ◽  
G. W. Cearley
Keyword(s):  
Cell Growth ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Seminal Vesicle ◽  
Seminal Vesicles ◽  
Epithelial Layer ◽  
Epithelial Hyperplasia ◽  
Electron Microscopic ◽  
Aging Rats ◽  
Pseudostratified Epithelium

It is well known that epithelial hyperplasia (benign hypertrophy) is common in the aging prostate of dogs and man. In contrast, little evidence is available for abnormal epithelial cell growth in seminal vesicles of aging animals. Recently, enlarged seminal vesicles were reported in senescent mice, however, that enlargement resulted from increased storage of secretion in the lumen and occurred concomitant to epithelial hypoplasia in that species.The present study is concerned with electron microscopic observations of changes occurring in the pseudostratified epithelium of the seminal vescles of aging rats. Special attention is given to certain non-epithelial cells which have entered the epithelial layer.

Rotary Beveling for In Situ Thin-Section Microscopy of Cell Cultures

1981 ◽  
Vol 39 ◽  
pp. 550-551
Author(s):  
Dean A. Handley ◽  
Jack T. Alexander ◽  
Shu Chien
Keyword(s):  
Cell Growth ◽  
Cell Cultures ◽  
Molecular Interactions ◽  
Convenient Method ◽  
Petri Dish ◽  
Simple Method ◽  
Thin Section Microscopy ◽  
Thin Sectioning ◽  
Organic Fluids

In situ preparation of cell cultures for ultrastructural investigations is a convenient method by which fixation, dehydration and embedment are carried out in the culture petri dish. The in situ method offers the advantage of preserving the native orientation of cell-cell interactions, junctional regions and overlapping configurations. In order to section after embedment, the petri dish is usually separated from the polymerized resin by either differential cryo-contraction or solvation in organic fluids. The remaining resin block must be re-embedded before sectioning. Although removal of the petri dish may not disrupt the native cellular geometry, it does sacrifice what is now recognized as an important characteristic of cell growth: cell-substratum molecular interactions. To preserve the topographic cell-substratum relationship, we developed a simple method of tapered rotary beveling to reduce the petri dish thickness to a dimension suitable for direct thin sectioning.

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