scholarly journals The Homeostasis of p62/SQSTM1 Short Isoform Regulates Selective Autophagy

Author(s):  
Chengcheng Wang ◽  
Hong Peng ◽  
Zi Wang ◽  
Jiao Yang ◽  
Chuanyin Li ◽  
...  

Abstract Autophagy, a highly conserved lysosomal degradation pathway, has been shown to play a pivotal role in many physiological and pathological processes. Sequestosome 1 (SQSTM1/p62) which serves as autophagy receptor is a multifunctional protein involved in signal transduction, protein degradation and cell transformation. Human SQSTM1 has two isoforms, p62L and p62S, which are derived from alternative splicing at the 5’donor sites. However, few studies focus on p62S, and its function needs to be further explored. Here we found that p62S, but not p62L is mainly degrades by ubiquitin-proteasome signaling pathway. E3 ligase TRIM72 was identified as an interacting partner for p62S, and promotes the ubiquitination and degradation of p62S. Furthermore, we demonstrate that p62S competes with the autophagy receptor p62L which binds to ubiquitinated autophagy cargoes, thus playing a dominant negative role in autophagy regulation, while this inhibitory effect could be attenuated by TRIM72-dependent ubiquitination of p62S. Delineation of the mechanism and regulatory roles of p62S sheds a new light on the proposed pathological implications of p62 in cell physiology. TRIM72 and p62S are promising therapeutic targets for autophagy-related diseases.

2008 ◽  
Vol 36 (3) ◽  
pp. 469-471 ◽  
Author(s):  
Robert Layfield ◽  
Mark S. Searle

A role for ubiquitin in the pathogenesis of human diseases was first suggested some two decades ago, from studies that localized the protein to intracellular protein aggregates, which are a feature of the major human neurodegenerative disorders. Although several different mechanisms have been proposed to connect impairment of the UPS (ubiquitin–proteasome system) to the presence of these ‘ubiquitin inclusions’ within diseased neurones, their significance in the disease process remains to be fully clarified. Ubiquitin inclusions also contain ubiquitin-binding proteins, such as the p62 protein [also known as SQSTM1 (sequestosome 1)], which non-covalently interacts with the ubiquitinated protein aggregates and may serve to mediate their autophagic clearance. p62 is a multifunctional protein and, in the context of bone-resorbing osteoclasts, is an important scaffold in the RANK [receptor activator of NF-κB (nuclear factor κB)]–NF-κB signalling pathway. Further, mutations affecting the UBA domain (ubiquitin-associated domain) of p62 are commonly found in patients with the skeletal disorder PDB (Paget's disease of bone). These mutations impair the ability of p62 to bind to ubiquitin and result in disordered osteoclast NF-κB signalling that may underlie the disease aetiology. Recent structural insights into the unusual mechanism of ubiquitin recognition by the p62 UBA domain have helped rationalize the mechanisms by which different PDB mutations exert their negative effects on ubiquitin binding by p62, as well as providing an indication of the ubiquitin-binding selectivity of p62 and, by extension, its normal biological functions.


2007 ◽  
Vol 179 (4) ◽  
pp. 2089-2096 ◽  
Author(s):  
Giovanna Peruzzi ◽  
Rosa Molfetta ◽  
Francesca Gasparrini ◽  
Laura Vian ◽  
Stefania Morrone ◽  
...  

2001 ◽  
Vol 280 (3) ◽  
pp. C441-C450 ◽  
Author(s):  
Edward D. Chan ◽  
David W. H. Riches

Nitric oxide (NO·) produced by inducible nitric oxide synthase (iNOS) mediates a number of important physiological and pathophysiological processes. The objective of this investigation was to examine the role of mitogen-activated protein kinases (MAPKs) in the regulation of iNOS and NO· by interferon-γ (IFN-γ) + lipopolysaccharide (LPS) in macrophages using specific inhibitors and dominant inhibitory mutant proteins of the MAPK pathways. The signaling pathway utilized by IFN-γ in iNOS induction is well elucidated. To study signaling pathways that are restricted to the LPS-signaling arm, we used a subclone of the parental RAW 264.7 cell line that is unresponsive to IFN-γ alone with respect to iNOS induction. In this RAW 264.7γNO(−) subclone, IFN-γ and LPS are nevertheless required for synergistic activation of the iNOS promoter. We found that extracellular signal-regulated kinase (ERK) augmented and p38 mapk inhibited IFN-γ + LPS induction of iNOS. Dominant-negative MAPK kinase-4 inhibited iNOS promoter activation by IFN-γ + LPS, also implicating the c-Jun NH2-terminal kinase (JNK) pathway in mediating iNOS induction. Inhibition of the ERK pathway markedly reduced IFN-γ + LPS-induced tumor necrosis factor-α protein expression, providing a possible mechanism by which ERK augments iNOS expression. The inhibitory effect of p38 mapk appears more complex and may be due to the ability of p38 mapk to inhibit LPS-induced JNK activation. These results indicate that the MAPKs are important regulators of iNOS-NO· expression by IFN-γ + LPS.


2021 ◽  
Author(s):  
Éva M. Szegõ ◽  
Eva M. Szegö ◽  
Chris Van den Haute ◽  
Lennart Höfs ◽  
Veerle Baekelandt ◽  
...  

Abstract BackgroundDuring the pathogenesis of Parkinson’s disease (PD), aggregation of alpha-synuclein (αSyn) induces a vicious cycle of cellular impairments that lead to neurodegeneration. Consequently, removing toxic αSyn aggregates constitutes a plausible strategy against PD. In this work, we tested whether stimulating the autolysosomal degradation of αSyn aggregates through the Ras-related in brain 7 (Rab7) pathway can reverse αSyn-induced cellular impairment and prevent neurodegeneration in vivo.MethodsThe disease-related A53T mutant of αSyn was expressed in primary neurons and in dopaminergic neurons of the rat brain simultaneously with wild type (WT) Rab7 or its dominant-negative T22N mutant as a control. The cellular integrity was quantified by morphological and biochemical analyses.ResultsIn primary neurons, WT Rab7 rescued the αSyn -induced loss of neurons and neurites. Furthermore, Rab7 decreased the amount of reactive oxygen species and the amount of Triton X-100 insoluble αSyn. In rat brain, WT Rab7 reduced αSyn -induced loss of dopaminergic axon terminals in the striatum and the loss of dopaminergic dendrites in the substantia nigra pars reticulata. Further, WT Rab7 lowered αSyn pathology as quantified by phosphorylated αSyn staining. Finally, WT Rab7 attenuated αSyn-induced DNA damage in primary neurons and rat brain.ConclusionRab7 reduced αSyn-induced pathology, ameliorated αSyn-induced neuronal degeneration, oxidative stress and DNA damage. These findings indicate that Rab7 is able to disrupt the vicious cycle of cellular impairment, αSyn pathology and neurodegeneration present in PD. Stimulation of Rab7 and the autolysosomal degradation pathway could therefore constitute a beneficial strategy for PD.


2008 ◽  
Vol 48 ◽  
pp. S162-S163
Author(s):  
J.D. Amaral ◽  
R.E. Castro ◽  
S. Sola ◽  
C.M.P. Rodrigues

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1485-1495 ◽  
Author(s):  
C.A. Micchelli ◽  
E.J. Rulifson ◽  
S.S. Blair

We have investigated the role of the Notch and Wingless signaling pathways in the maintenance of wing margin identity through the study of cut, a homeobox-containing transcription factor and a late-arising margin-specific marker. By late third instar, a tripartite domain of gene expression can be identified about the dorsoventral compartment boundary, which marks the presumptive wing margin. A central domain of cut- and wingless-expressing cells are flanked on the dorsal and ventral side by domains of cells expressing elevated levels of the Notch ligands Delta and Serrate. We show first that cut acts to maintain margin wingless expression, providing a potential explanation of the cut mutant phenotype. Next, we examined the regulation of cut expression. Our results indicate that Notch, but not Wingless signaling, is autonomously required for cut expression. Rather, Wingless is required indirectly for cut expression; our results suggest this requirement is due to the regulation by wingless of Delta and Serrate expression in cells flanking the cut and wingless expression domains. Finally, we show that Delta and Serrate play a dual role in the regulation of cut and wingless expression. Normal, high levels of Delta and Serrate can trigger cut and wingless expression in adjacent cells lacking Delta and Serrate. However, high levels of Delta and Serrate also act in a dominant negative fashion, since cells expressing such levels cannot themselves express cut or wingless. We propose that the boundary of Notch ligand along the normal margin plays a similar role as part of a dynamic feedback loop that maintains the tripartite pattern of margin gene expression.


1993 ◽  
Vol 13 (12) ◽  
pp. 7645-7651
Author(s):  
H Cai ◽  
P Erhardt ◽  
J Troppmair ◽  
M T Diaz-Meco ◽  
G Sithanandam ◽  
...  

We have investigated the relationship between hydrolysis of phosphatidylcholine (PC) and activation of the Raf-1 protein kinase in Ras-mediated transduction of mitogenic signals. As previously reported, cotransfection of a PC-specific phospholipase C (PC-PLC) expression plasmid bypassed the block to cell proliferation resulting from expression of the dominant inhibitory mutant Ras N-17. In contrast, PC-PLC failed to bypass the inhibitory effect of dominant negative Raf mutants, suggesting that PC-PLC functions downstream of Ras but upstream of Raf. Consistent with this hypothesis, treatment of quiescent cells with exogenous PC-PLC induced Raf activation, even when normal Ras function was blocked by Ras N-17 expression. Further, activation of Raf in response to mitogenic growth factors was blocked by inhibition of endogenous PC-PLC. Taken together, these results indicate that hydrolysis of PC mediates Raf activation in response to mitogenic growth factors.


1999 ◽  
Vol 19 (3) ◽  
pp. 2300-2307 ◽  
Author(s):  
Chi-Wing Chow ◽  
Mercedes Rincón ◽  
Roger J. Davis

ABSTRACT The nuclear factor of activated T cells (NFAT) transcription factor is implicated in expression of the cytokine interleukin-2 (IL-2). Binding sites for NFAT are located in the IL-2 promoter. Furthermore, pharmacological studies demonstrate that the drug cyclosporin A inhibits both NFAT activation and IL-2 expression. However, targeted disruption of the NFAT1 and NFAT2 genes in mice does not cause decreased IL-2 secretion. The role of NFAT in IL-2 gene expression is therefore unclear. Here we report the construction of a dominant-negative NFAT mutant (dnNFAT) that selectively inhibits NFAT-mediated gene expression. The inhibitory effect of dnNFAT is mediated by suppression of activation-induced nuclear translocation of NFAT. Expression of dnNFAT in cultured T cells caused inhibition of IL-2 promoter activity and decreased expression of IL-2 protein. Similarly, expression of dnNFAT in transgenic mice also caused decreased IL-2 gene expression. These data demonstrate that NFAT is a critical component of the signaling pathway that regulates IL-2 expression.


1994 ◽  
Vol 14 (10) ◽  
pp. 6655-6662 ◽  
Author(s):  
N Yamauchi ◽  
A A Kiessling ◽  
G M Cooper

We have used microinjection of antisense oligonucleotides, monoclonal antibody, and the dominant negative Ras N-17 mutant to interfere with Ras expression and function in mouse oocytes and early embryos. Microinjection of either ras antisense oligonucleotides or anti-Ras monoclonal antibody Y13-259 did not affect normal progression of oocytes through meiosis and arrest at metaphase II. However, microinjection of fertilized eggs with constructs expressing Ras N-17 inhibited subsequent development through the two-cell stage. The inhibitory effect of Ras N-17 was overcome by simultaneous injection of a plasmid expressing an active raf oncogene, indicating that it resulted from interference with the Ras/Raf signaling pathway. In contrast to the inhibition of two-cell embryo development resulting from microinjection of pronuclear stage eggs, microinjection of late two-cell embryos with Ras N-17 expression constructs did not affect subsequent cleavages and development to morulae and blastocysts. It thus appears that the Ras/Raf signaling pathway, presumably activated by autocrine growth factor stimulation, is specifically required at the two-cell stage, which is the time of transition between maternal and embryonic gene expression in mouse embryos.


2000 ◽  
Vol 20 (19) ◽  
pp. 7068-7079 ◽  
Author(s):  
Carole Peyssonnaux ◽  
Sylvain Provot ◽  
Marie Paule Felder-Schmittbuhl ◽  
Georges Calothy ◽  
Alain Eychène

ABSTRACT Ras-induced cell transformation is mediated through distinct downstream signaling pathways, including Raf, Ral-GEFs-, and phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathways. In some cell types, strong activation of the Ras–Raf–MEK–extracellular signal-regulated kinase (ERK) cascade leads to cell cycle arrest rather than cell division. We previously reported that constitutive activation of this pathway induces sustained proliferation of primary cultures of postmitotic chicken neuroretina (NR) cells. We used this model system to investigate the respective contributions of Ras downstream signaling pathways in Ras-induced cell proliferation. Three RasV12 mutants (S35, G37, and C40) which differ by their ability to bind to Ras effectors (Raf, Ral-GEFs, and the p110 subunit of PI 3-kinase, respectively) were able to induce sustained NR cell proliferation, although none of these mutants was reported to transform NIH 3T3 cells. Furthermore, they all repressed the promoter of QR1, a neuroretina growth arrest-specific gene. Overexpression of B-Raf or activated versions of Ras effectors Rlf-CAAX and p110-CAAX also induced NR cell division. The mitogenic effect of the RasC40–PI 3-kinase pathway appears to involve Rac and RhoA GTPases but not the antiapoptotic Akt (protein kinase B) signaling. Division induced by RasG37-Rlf appears to be independent of Ral GTPase activation and presumably requires an unidentified mechanism. Activation of either Ras downstream pathway resulted in ERK activation, and coexpression of a dominant negative MEK mutant or mKsr-1 kinase domain strongly inhibited proliferation induced by the three Ras mutants or by their effectors. Similar effects were observed with dominant negative mutants of Rac and Rho. Thus, both the Raf-MEK-ERK and Rac-Rho pathways are absolutely required for Ras-induced NR cell division. Activation of these two pathways by the three distinct Ras downstream effectors possibly relies on an autocrine or paracrine loop, implicating endogenous Ras, since the mitogenic effect of each Ras effector mutant was inhibited by RasN17.


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