MIR Is a Novel ERM-like Protein That Interacts with Myosin Regulatory Light Chain and Inhibits Neurite Outgrowth

Olsson, Per-Anders; Korhonen, Laura; Mercer, Eric A.; Lindholm, Dan

doi:10.1074/jbc.274.51.36288

Cited by 72 publications

(78 citation statements)

References 31 publications

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“…Northern Blot Analysis-Multiple Tissue Northern (MTN TM ) blots (Clontech) were prehybridized for 30 min at 68°C using ULTRAhyb (Ambion) and hybridized at 68°C overnight using 10 6 cpm/ml of the MSAP cRNA probe (15). Filters were washed, and the levels of MSAP mRNA were analyzed using a PhosphorImager (Amersham Biosciences) and compared with those of ␤-actin.…”

Section: Methodsmentioning

confidence: 99%

“…Cloning of MSAP and Expression Constructs-MSAP DNA was amplified by PCR and used for screening of a gt10 human fetal brain library (Clontech) (15). Positive clones were subcloned into the Bluescript pKS vector (Stratagene) and sequenced using an automated DNA sequencer (Applied Biosystems).…”

Section: Methodsmentioning

confidence: 99%

“…Yeast Two-hybrid System-The full-length coding sequence of MIR was fused to the GAL4 DNA-binding domain in the pYTH6 bait vector and used for screening a cDNA library of HeLa cells (Clontech) (15,18). Clones positive for interaction were sequenced, and twelve were identified as MSAP.…”

Section: Methodsmentioning

confidence: 99%

“…We have recently identified a novel ERM family protein, MIR, which has an ERM domain at the N terminus and lacks actin binding, instead possessing a RING domain in the Cterminal region (15). Overexpression of MIR abrogated neurite outgrowth in PC12 cells, an effect that may be brought about by its interaction with the myosin regulatory light chain (MRLC).…”

mentioning

confidence: 99%

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MSAP Is a Novel MIR-interacting Protein That Enhances Neurite Outgrowth and Increases Myosin Regulatory Light Chain

Bornhäuser¹,

Olsson

Lindholm

2003

Journal of Biological Chemistry

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Interactions between the cell membrane and the cytoskeleton play a major role in different aspects of cell differentiation, such as cell motility, cell division, and establishment of cellular architecture. Of particular importance in this context is the association of cortical actin with the cell membrane. The ERM 1 proteins, ezrin, radixin, and moesin, are members of the large 4.1 protein family and are involved in membrane-cytoskeleton interactions. They link the actin cytoskeleton to membranebound proteins located at different membrane sites, i.e. microvilli, membrane ruffles, and cell-cell contacts (1-3). This is accomplished by binding of the C-terminal part of the ERM proteins to actin and of the N-terminal FERM domain to specific membrane proteins (4). FERM domains have been found in many different proteins and are thought to be modules for protein-protein and protein-membrane interactions (5). The ERM proteins are involved in cell adhesion and signal transduction events through phosphorylation (6, 7) and interaction with phosphoinositides (8). The ERM proteins play an important role in the activation of Rho family proteins and can interact both downstream (9) and upstream (10) of Rho.In addition, the ERM proteins are involved in membrane dynamics (11). When ezrin, radixin, and moesin were simultaneously inactivated by antisense treatment in epithelial cells, cell-cell and cell-substratum adhesion was altered (12). Double suppression of radixin and moesin, but not ezrin and radixin or moesin, alters growth cone motility, inhibiting neurite extension (13). In contrast, overexpression of ezrin in insect cells leads to enhanced cell adhesion (14). The mechanisms behind these effects are, however, not well understood, but ERM proteins are known to interact with various proteins such as CD44 and ICAM-1, -2, and -3, which helps in establishing membrane specializations (for review, see Ref. 7). The identification and characterization of further binding partners for ERM proteins can give new insights into the function of these proteins.We have recently identified a novel ERM family protein, MIR, which has an ERM domain at the N terminus and lacks actin binding, instead possessing a RING domain in the Cterminal region (15). Overexpression of MIR abrogated neurite outgrowth in PC12 cells, an effect that may be brought about by its interaction with the myosin regulatory light chain (MRLC). We describe here a novel protein interacting with MIR, called MIR-interacting saposin-like protein (MSAP), which stimulates neurite outgrowth. Sequence comparisons showed that MSAP contains a saposin domain, which is found, among others, in the sphingolipid activator proteins, the saposins (16), and in some saposin-like proteins with a similar structure (17). The effects of MSAP on neurite outgrowth were reduced by MIR. MIR was shown to induce a decrease in the levels of MRLC, which could be blocked by overexpression of MSAP or by inhibition of proteasome activity. Evidence was obtained that the decrease in MRLC levels by MIR invo...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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MSAP Is a Novel MIR-interacting Protein That Enhances Neurite Outgrowth and Increases Myosin Regulatory Light Chain

Bornhäuser¹,

Olsson

Lindholm

2003

Journal of Biological Chemistry

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“…Accordingly, mice lacking these receptors have developmental problems (57). IDOL is highly expressed in the brain (58), and unlike other LXR targets (e.g. ABCA1) is not subject to LXR-dependent regulation in neurons (27).…”

Section: Lxr␣␤mentioning

confidence: 99%

Deubiquitylase Inhibition Reveals Liver X Receptor-independent Transcriptional Regulation of the E3 Ubiquitin Ligase IDOL and Lipoprotein Uptake

Nelson

Cook

Loregger

et al. 2016

Journal of Biological Chemistry

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Cholesterol metabolism is subject to complex transcriptional and nontranscriptional regulation. Herein, the role of ubiquitylation is emerging as an important post-translational modification that regulates cholesterol synthesis and uptake. Similar to other post-translational modifications, ubiquitylation is reversible in a process dependent on activity of deubiquitylating enzymes (DUBs). Yet whether these play a role in cholesterol metabolism is largely unknown. As a first step to test this possibility, we used pharmacological inhibition of cellular DUB activity. Short term (2 h) inhibition of DUBs resulted in accumulation of high molecular weight ubiquitylated proteins. This was accompanied by a dramatic decrease in abundance of the LDLR and attenuated LDL uptake into hepatic cells. Importantly, this occurred in the absence of changes in the mRNA levels of the LDLR or other SREBP2-regulated genes, in line with this phenotype being a post-transcriptional event. Mechanistically, we identify transcriptional induction of the E3 ubiquitin ligase IDOL in human and rodent cells as the underlying cause for ubiquitylation-dependent lysosomal degradation of the LDLR following DUB inhibition. In contrast to the established transcriptional regulation of IDOL by the sterol-responsive liver X receptor (LXR) transcription factors, induction of IDOL by DUB inhibition is LXR-independent and occurs in Lxr␣␤ ؊/؊ MEFs.Consistent with the role of DUBs in transcriptional regulation, we identified a 70-bp region in the proximal promoter of IDOL, distinct from that containing the LXR-responsive element, which mediates the response to DUB inhibition. In conclusion, we identify a sterol-independent mechanism to regulate IDOL expression and IDOL-mediated lipoprotein receptor degradation.Elevated levels of plasma LDL represent a major risk factor for development of atherosclerosis and cardiovascular disease (1). Because of its ability to promote LDL uptake into cells, the LDL receptor (LDLR) 2 is a major determinant of plasma LDL levels (2). The pivotal role of the LDLR in LDL metabolism is exemplified by the fact that LDLR mutations account for most incidences of familial hypercholesterolemia, a disease characterized by reduced hepatic LDL clearance, elevated plasma cholesterol levels, and accelerated cardiovascular disease (1, 3).The LDLR is subject to tight transcriptional and post-transcriptional regulation, which is largely governed by the intracellular levels of cholesterol (4). At the level of transcription, these pathways are regulated by two nuclear transcription factor families: SREBP1 and SREBP2 (5-7), and the liver X receptor ␣ and ␤ (LXRs) (8, 9). When cellular sterol levels decline, SREBPs are activated to induce genes required for de novo cholesterol biosynthesis, as well as the LDLR to increase uptake of LDL cholesterol (4). In contrast, when sterol levels rise, LXRs become activated by their endogenous ligands. These ligands include oxidized cholesterol derivatives (oxysterols) and intermediates of the cholesterol synthes...

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LDL Receptor and Its Role in Inherited Disease

Soutar

2010

Encyclopedia of Life Sciences

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The low‐density lipoprotein (LDL) receptor mediates the specific uptake of LDL from the circulation and its intracellular degradation by a process known as the LDL receptor pathway. LDL receptor gene expression is regulated by intracellular sterol content, and is limited mainly to the liver in vivo . Mutations in LDLR , the gene encoding the LDL receptor, cause familial hypercholesterolaemia (FH), a dominantly inherited disease where accumulation of LDL in the circulation increases the risk of coronary heart disease. Defects in other genes, including APOB , encoding the ligand for the LDL receptor, ARH , encoding a protein required for its internalisation and proprotein convertase subtilisin/kexin type 9 ( PCSK9 ), encoding a protein that reduces LDL receptor protein levels, cause a similar disorder because the encoded proteins are involved in the LDL receptor pathway. FH can readily be treated with cholesterol‐lowering drugs to reduce cardiovascular risk effectively, and identification of the causal genetic defect allows unequivocal and early diagnosis. Key Concepts: The LDL receptor mediates specific uptake and intracellular degradation of serum LDL. Inherited defects in the LDL receptor pathway cause familial hypercholesterolaemia (FH), characterised by increased serum LDL and increased risk of coronary heart disease. Most FH patients have mutations in LDLR , but defects in other genes cause a similar disorder. A recessive form of FH is caused by null mutations in ARH, a clathrin adaptor protein required for LDL receptor internalisation. A dominant form of FH is caused by gain‐of‐function mutations in PCSK9 , which encodes a protein that promotes degradation of LDL receptor protein. Dominant loss‐of‐function mutations in PCSK9 reduce serum cholesterol and risk of coronary heart disease. One relatively common dominant mutation in APOB , encoding the ligand for the LDL receptor, causes familial defective apoB (FDB). LDLR transcription is regulated by sterol response element‐binding proteins (SREBP) in a complex mechanism involving several other proteins. FH can readily be treated with cholesterol‐lowering drug therapy to abolish the increased risk of coronary disease, but is currently under‐diagnosed. Identifying causal mutations in known patients and screening their relatives should identify more affected individuals.

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MIR Is a Novel ERM-like Protein That Interacts with Myosin Regulatory Light Chain and Inhibits Neurite Outgrowth

Cited by 72 publications

References 31 publications

MSAP Is a Novel MIR-interacting Protein That Enhances Neurite Outgrowth and Increases Myosin Regulatory Light Chain

MSAP Is a Novel MIR-interacting Protein That Enhances Neurite Outgrowth and Increases Myosin Regulatory Light Chain

Deubiquitylase Inhibition Reveals Liver X Receptor-independent Transcriptional Regulation of the E3 Ubiquitin Ligase IDOL and Lipoprotein Uptake

LDL Receptor and Its Role in Inherited Disease

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