scholarly journals Bulk degradation of dendritic cargos requires Rab7-dependent transport in Rab7-positive/LAMP1-negative endosomes to somatic lysosomes

2017 ◽  
Author(s):  
C.C. Yap ◽  
L. Digilio ◽  
L.P. McMahon ◽  
A.D.R. Garcia ◽  
B. Winckler
Keyword(s):  
Membrane Proteins ◽  
Protein Turnover ◽  
Cellular Stress ◽  
Distal Portion ◽  
Proximal Portion ◽  
Spatial Gradient ◽  
Protein Homeostasis ◽  
Late Endosomes ◽  
Dendritic Membrane ◽  
Dependent Transport

AbstractRegulation of protein homeostasis (“proteostasis”) is necessary for maintaining healthy cells. Disturbances in proteostasis lead to aggregates, cellular stress and can result in toxicity. There is thus great interest in when and where proteins are degraded in cells. Neurons are very large as well as very long-lived, creating unusually high needs for effective regulation of protein turnover in time and space. We previously discovered that the dendritic membrane proteins Nsg1 and Nsg2 are short-lived with half-lives of less than two hours. Their short half-lives enabled us to ask whether these proteins are degraded by local degradative pathways in dendrites. We discovered a striking spatial gradient of late endosomes/lysosomes in dendrites, with late endosomes (Rab7-positive/LAMP1-negative/cathepsinB-negative) found in distal portion of dendrites, and degradative lysosomes (LAMP1-positive/cathepsinB-positive) being overwhelmingly found in the soma and in the proximal portion of dendrites. Surprisingly, the majority of dendritic Rab7-positive late endosomes do not contain LAMP1, unlike Rab7-positive late endosomes in fibroblasts. Secondly, Rab7 activity is required to mobilize these distal pre-degradative dendritic late endosomes for transport to the soma and degradation. We conclude that the vast majority of dendritic LAMP1-positive endosomes are not degradative lysosomes and that bulk degradation of dendritic cargos, such as Nsg1, Nsg2, and DNER, requires Rab7-dependent transport in late endosomes to somatic lysosomes.

scholarly journals Degradation of dendritic cargos requires Rab7-dependent transport to somatic lysosomes

2018 ◽  
Vol 217 (9) ◽  
pp. 3141-3159 ◽  
Author(s):  
Chan Choo Yap ◽  
Laura Digilio ◽  
Lloyd P. McMahon ◽  
A. Denise R. Garcia ◽  
Bettina Winckler
Keyword(s):  
Membrane Proteins ◽  
Spatial Heterogeneity ◽  
Protein Turnover ◽  
Cellular Stress ◽  
Proximal Segment ◽  
Late Endosomes ◽  
Dendritic Membrane ◽  
Dependent Transport

Neurons are large and long lived, creating high needs for regulating protein turnover. Disturbances in proteostasis lead to aggregates and cellular stress. We characterized the behavior of the short-lived dendritic membrane proteins Nsg1 and Nsg2 to determine whether these proteins are degraded locally in dendrites or centrally in the soma. We discovered a spatial heterogeneity of endolysosomal compartments in dendrites. Early EEA1-positive and late Rab7-positive endosomes are found throughout dendrites, whereas the density of degradative LAMP1- and cathepsin (Cat) B/D–positive lysosomes decreases steeply past the proximal segment. Unlike in fibroblasts, we found that the majority of dendritic Rab7 late endosomes (LEs) do not contain LAMP1 and that a large proportion of LAMP1 compartments do not contain CatB/D. Second, Rab7 activity is required to mobilize distal predegradative LEs for transport to the soma and terminal degradation. We conclude that the majority of dendritic LAMP1 endosomes are not degradative lysosomes and that terminal degradation of dendritic cargos such as Nsg1, Nsg2, and DNER requires Rab7-dependent transport in LEs to somatic lysosomes.

Complete Endoscopic Carpal Tunnel Release in Long-Term Haemodialysis Patients

1996 ◽  
Vol 21 (5) ◽  
pp. 668-671 ◽  
Author(s):  
I. OKUTSU ◽  
I. HAMANAKA ◽  
T. TANABE ◽  
Y. TAKATORI ◽  
S. NINOMIYA
Keyword(s):  
Carpal Tunnel ◽  
Carpal Tunnel Release ◽  
Distal Portion ◽  
Proximal Portion ◽  
Flexor Retinaculum ◽  
Endoscopic Release ◽  
Before And After ◽  
Tunnel Syndrome ◽  
Infusion Technique

The roof of the carpal tunnel (or canal) consists of the distal portion of the flexor retinaculum, the flexor retinaculum (or the transverse carpal ligament) and the proximal portion of the flexor retinaculum. We tried to determine which anatomical structures were relevant to complete endoscopic carpal tunnel decompression in long-term haemodialysis patients with carpal tunnel syndrome. Carpal tunnel pressure was measured using the continuous infusion technique before and after endoscopic release of the flexor retinaculum, distal portion of the flexor retinaculum and the proximal portion of the flexor retinaculum respectively in 257 hands. We concluded that release of the distal portion of the flexor retinaculum, in addition to the flexor retinaculum, is essential for complete carpal tunnel decompression in long-term haemodialysis patients.

scholarly journals Tipos de Derrame e Reconhecimento de Estruturas nos Basaltos da Formação Serra Geral: Terminologia e Aspectos de Campo

2006 ◽  
Vol 33 (2) ◽  
pp. 123 ◽  
Author(s):  
BRENO LEITÃO WAICHEL ◽  
EVANDRO FERNANDES DE LIMA ◽  
CARLOS AUGUSTO SOMMER
Keyword(s):  
Columbia River ◽  
Distal Portion ◽  
Proximal Portion ◽  
Lateral Extension ◽  
Hawaiian Archipelago ◽  
Columbia River Basalts ◽  
Surface Features ◽  
Flow Morphology ◽  
Deccan Plateau

Studies focusing the flow morphology and structures of the basalts of Serra Geral Formation (west of Paraná State, Brazil) make possible the identification of pahoehoe and 'a'a flows, with predominance of simple and compound pahoehoe. This terminology was created in the Hawaiian Archipelago and was previously applied to the Columbia River Basalts and Deccan Plateau, and can also be used in the investigation of the Serra Geral Formation. The compound pahoehoe flows are formed by Ptype (pipe) and S-type (spongy) lobes. Surface features related with the pahoehoe and aa flows are well preserved in Serra Geral Formation. The flows have lateral extension of up to 50 km and can be divided in three portions in relation to the conduit: proximal, medium and distal. In the proximal portion the flows are thick (40-70 m) and the contact between the superior crust and the massive core is sharp. In the medium portion predominate simple pahoehoe flows with thickness between 20 and 30 m; locally occur compound pahoehoe. The distal portion is formed by compound flows (up to 5 m thick) with a few lobes. The emplacement of the pahoehoe inflated flows in the studied area suggests low eruption rates.

scholarly journals Crosstalk and ultrasensitivity in protein degradation pathways

2020 ◽  
Vol 16 (12) ◽  
pp. e1008492
Author(s):  
Abhishek Mallela ◽  
Maulik K. Nariya ◽  
Eric J. Deeds
Keyword(s):  
Protein Turnover ◽  
E3 Ligase ◽  
Biochemical Networks ◽  
Protein Homeostasis ◽  
Polyubiquitin Chain ◽  
Post Translational Modification ◽  
E3 Ligases ◽  
Protein Levels ◽  
Synthesis And Degradation

Protein turnover is vital to cellular homeostasis. Many proteins are degraded efficiently only after they have been post-translationally “tagged” with a polyubiquitin chain. Ubiquitylation is a form of Post-Translational Modification (PTM): addition of a ubiquitin to the chain is catalyzed by E3 ligases, and removal of ubiquitin is catalyzed by a De-UBiquitylating enzyme (DUB). Nearly four decades ago, Goldbeter and Koshland discovered that reversible PTM cycles function like on-off switches when the substrates are at saturating concentrations. Although this finding has had profound implications for the understanding of switch-like behavior in biochemical networks, the general behavior of PTM cycles subject to synthesis and degradation has not been studied. Using a mathematical modeling approach, we found that simply introducing protein turnover to a standard modification cycle has profound effects, including significantly reducing the switch-like nature of the response. Our findings suggest that many classic results on PTM cycles may not hold in vivo where protein turnover is ubiquitous. We also found that proteins sharing an E3 ligase can have closely related changes in their expression levels. These results imply that it may be difficult to interpret experimental results obtained from either overexpressing or knocking down protein levels, since changes in protein expression can be coupled via E3 ligase crosstalk. Understanding crosstalk and competition for E3 ligases will be key in ultimately developing a global picture of protein homeostasis.

scholarly journals Strain-Dependent Recognition of a Unique Degradation Motif by ClpXP in Streptococcus mutans

mSphere ◽  
2016 ◽  
Vol 1 (6) ◽  
Author(s):  
Biswanath Jana ◽  
Liang Tao ◽  
Indranil Biswas
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Streptococcus Mutans ◽  
Protein Turnover ◽  
Fluorescent Protein ◽  
Biological Process ◽  
Polyacrylamide Gel Electrophoresis ◽  
Adaptor Protein ◽  
Protein Homeostasis ◽  
Content Type

ABSTRACT Regulated proteolysis in bacteria is an important biological process that maintains protein homeostasis. ClpXP, an intracellular proteolytic complex, is the primary protease that is responsible for protein turnover. While the substrates for ClpXP were identified in Escherichia coli, the substrates for vast majority of bacteria are currently unknown. In this study, we identified a unique substrate for ClpXP-mediated degradation in Streptococcus mutans, a dental pathogen. We also found that a small motif composed of 3 amino acids is sufficient for ClpXP-mediated degradation. Identification of this motif will clearly help us to understand the pathogenesis of this organism and other related pathogens. Streptococcus mutans, a dental pathogen, has a remarkable ability to cope with environmental stresses. Under stress conditions, cytoplasmic proteases play a major role in controlling the stability of regulatory proteins and preventing accumulation of damaged and misfolded proteins. ClpXP, a well-conserved cytoplasmic proteolytic system, is crucial in maintaining cellular homeostasis in bacteria. ClpX is primarily responsible for recognition of substrates and subsequent translocation of unfolded substrates into the ClpP proteolytic compartment for degradation. In Escherichia coli, ClpX recognizes distinct motifs present at the C-terminal end of target proteins. However, recognition sequences for ClpXP in other bacteria, including S. mutans, are not known. In this study, using two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) analysis, we have identified several putative substrates for S. mutans ClpXP. SsbA, which encodes a small DNA binding protein, is one such substrate that is degraded by ClpXP. By sequential deletions, we found that the last 3 C-terminal amino acids, LPF, are sufficient for ClpXP-mediated degradation. Addition of LPF at the C-terminal end of green fluorescent protein (GFP) rendered the protein completely degradable by ClpXP. Alterations of this tripeptide motif impeded ClpXP-mediated degradation. However, recognition of LPF by ClpXP is highly specific to some S. mutans strains (UA159, UA130, and N3209) since not all S. mutans strains recognize the motif. We speculate that an adaptor protein is involved in either substrate recognition or substrate degradation by ClpXP. Nevertheless, this is the first report of a unique recognition sequence for ClpXP in streptococci. IMPORTANCE Regulated proteolysis in bacteria is an important biological process that maintains protein homeostasis. ClpXP, an intracellular proteolytic complex, is the primary protease that is responsible for protein turnover. While the substrates for ClpXP were identified in Escherichia coli, the substrates for vast majority of bacteria are currently unknown. In this study, we identified a unique substrate for ClpXP-mediated degradation in Streptococcus mutans, a dental pathogen. We also found that a small motif composed of 3 amino acids is sufficient for ClpXP-mediated degradation. Identification of this motif will clearly help us to understand the pathogenesis of this organism and other related pathogens.

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