Lamin A/C and emerin regulate MKL1–SRF activity by modulating actin dynamics

Chuang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2015

115

The sigma-1 receptor (Sig-1R) chaperone at the endoplasmic reticulum (ER) plays important roles in cellular regulation. Here we found a new function of Sig-1R, in that it translocates from the ER to the nuclear envelope (NE) to recruit chromatin-remodeling molecules and regulate the gene transcription thereof. Sig-1Rs mainly reside at the ER-mitochondrion interface. However, on stimulation by agonists such as cocaine, Sig-1Rs translocate from ER to the NE, where Sig-1Rs bind NE protein emerin and recruit chromatin-remodeling molecules, including lamin A/C, barrier-to-autointegration factor (BAF), and histone deacetylase (HDAC), to form a complex with the gene repressor specific protein 3 (Sp3). Knockdown of Sig-1Rs attenuates the complex formation. Cocaine was found to suppress the gene expression of monoamine oxidase B (MAOB) in the brain of wild-type but not Sig-1R knockout mouse. A single dose of cocaine (20 mg/kg) in rats suppresses the level of MAOB at nuclear accumbens without affecting the level of dopamine transporter. Daily injections of cocaine in rats caused behavioral sensitization. Withdrawal from cocaine in cocaine-sensitized rats induced an apparent time-dependent rebound of the MAOB protein level to about 200% over control on day 14 after withdrawal. Treatment of cocaine-withdrawn rats with the MAOB inhibitor deprenyl completely alleviated the behavioral sensitization to cocaine. Our results demonstrate a role of Sig-1R in transcriptional regulation and suggest cocaine may work through this newly discovered genomic action to achieve its addictive action. Results also suggest the MAOB inhibitor deprenyl as a therapeutic agent to block certain actions of cocaine during withdrawal.T he endoplasmic reticulum (ER) plays important roles in cellular functions, including synthesis of proteins and regulation of Ca 2+ signaling between the ER and plasma membrane (1) and between the ER and mitochondria (2-4). However, because the ER interacts with other organelles in the cell, other functions related to the ER remain to be uncovered.The sigma-1 receptor (Sig-1R) (5-8) is an ER chaperone molecule that resides at the ER-mitochondrion interface referred to as the mitochondria-associated ER membrane (MAM), where the Sig-1R ensures proper ER-mitochondrion Ca 2+ signaling for cellular survival (3, 9), as well as sustains the activity of an ER stress sensor IRE1 at the MAM (10). The Sig-1R can translocate from the MAM to plasma membrane of the cell to regulate ion channels and receptors on the plasma membrane (8,(11)(12)(13)(14). Cocaine is a Sig-1R agonist (3) that causes the dissociation of Sig-1R from its cognate binding partner BiP (3,8), and consequently the translocation of Sig-1Rs to the plasma membrane, where Sig-1Rs interact with voltage-gated potassium channel subfamily A member 2 (Kv1.2) to shape the neuronal and behavioral responses to cocaine (15).Cocaine also causes the translocation of Sig-1Rs from the ER to the nucleus (16), where Sig-1Rs are shown to be present at the nuclear envelope (NE) (17). H...

Section: Significancementioning

confidence: 99%

Sigma-1 receptor mediates cocaine-induced transcriptional regulation by recruiting chromatin-remodeling factors at the nuclear envelope

Chuang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2015

115

Proc. Natl. Acad. Sci. U.S.A.

“…This complex provides a physical connection between the cytoskeleton and the nucleoplasm and hence is named the "LINC" (linker of the nucleoskeleton and cytoskeleton) complex (14,15). This physical structure allows mechanical transduction from the cytoskeleton directly into the nucleus.…”

mentioning

confidence: 99%

“…Nuclear lamin A/C and emerin are important components of the inner nuclear membrane (INM) that link with chromatin and participate in the spatial organization of chromosomes and gene transcription (14,15). Defects in lamins or emerin cause a…”

mentioning

confidence: 99%

Nuclear envelope proteins modulate proliferation of vascular smooth muscle cells during cyclic stretch application

Yao

Huang

et al. 2016

Cyclic stretch is an important inducer of vascular smooth muscle cell (VSMC) proliferation, which is crucial in vascular remodeling during hypertension. However, the molecular mechanism remains unclear. We studied the effects of emerin and lamin A/C, two important nuclear envelope proteins, on VSMC proliferation in hypertension and the underlying mechano-mechanisms. In common carotid artery of hypertensive rats in vivo and in cultured cells subjected to high (15%) cyclic stretch in vitro, VSMC proliferation was increased significantly, and the expression of emerin and lamin A/C was repressed compared with normotensive or normal (5%) cyclic stretch controls. Using targeted siRNA to mimic the repressed expression of emerin or lamin A/C induced by 15% stretch, we found that VSMC proliferation was enhanced under static and 5%-stretch conditions. Overexpression of emerin or lamin A/C reversed VSMC proliferation induced by 15% stretch. Hence, emerin and lamin A/C play critical roles in suppressing VSMC hyperproliferation induced by hyperstretch. ChIP-on-chip and MOTIF analyses showed that the DNAs binding with emerin contain three transcription factor motifs: CCNGGA, CCMGCC, and ABTTCCG; DNAs binding with lamin A/C contain the motifs CVGGAA, GCCGCYGC, and DAAGAAA. Protein/DNA array proved that altered emerin or lamin A/C expression modulated the activation of various transcription factors. Furthermore, accelerating local expression of emerin or lamin A/C reversed cell proliferation in the carotid artery of hypertensive rats in vivo. Our findings establish the pathogenetic role of emerin and lamin A/C repression in stretch-induced VSMC proliferation and suggest mechanobiological mechanism underlying this process that involves the sequencespecific binding of emerin and lamin A/C to specific transcription factor motifs.T he cyclic stretch caused by the rhythmical distention and relaxation of the arterial wall during the cardiac cycle is an important factor in the regulation of vascular modeling and remodeling (1, 2). There is growing evidence that mechanical cyclic stretch modulates the functions (e.g., apoptosis, proliferation, and migration) of vascular smooth muscle cells (VSMCs) in the media of the arterial wall (2) and that chronically elevated cyclic stretch stimulates VSMC functions to mediate vascular remodeling during hypertension (3, 4).It has been shown that there are various mechano-sensors in the vascular cell membrane, including lipids (5), glycocalyx (6), and proteins such as integrins (7), G proteins and G protein-coupled receptors (8), receptor tyrosine kinase (9), and Ca 2+ channel (10) and intercellular junction proteins (2, 11). In recent years, it has been suggested that nuclear envelope (NE) proteins, a hallmark of eukaryotic cells, participate in the mechano-transduction networks. Our previous proteomic analysis revealed that lamin A/C, one kind of NE protein, is mechano-responsive and may contribute to the shear stress-induced proliferation and migration of VSMCs (12). Recently, Swift et al. (13) ...

“…These SRF coactivators are interacting with G-actin and translocate to the nucleus 17 , when G-actin levels decrease, for example, due to sequestration by the G-actinbinding peptide thymosin 4 (T 4) [18][19][20] . Since T 4 is a potent pro-angiogenic factor 21 , an involvement of the T 4-MRTF-SRF axis in vascular growth would require transcriptional activation beyond well-known myogenic proteins 13,14 . However, MRTF coactivaton of SRF induces pro-angiogenic factors such as CCN1 (Cyr61) 22 and maturation factors such as connective tissue growth factor (CTGF) 23,24 .…”

mentioning

confidence: 99%

“…Myocardin-related transcription factors (MRTFs) have been shown to activate serum response factor (SRF) [9][10][11] upon dissociation from G-actin 12 , providing muscle growth and regeneration 13,14 . SRF is co-activated by myocardin 15 or MRTFs A and B 16 .…”

mentioning

confidence: 99%

MRTF-A controls vessel growth and maturation by increasing the expression of CCN1 and CCN2

et al. 2014

Gradual occlusion of coronary arteries may result in reversible loss of cardiomyocyte function (hibernating myocardium), which is amenable to therapeutic neovascularization. The role of myocardin-related transcription factors (MRTFs) co-activating serum response factor (SRF) in this process is largely unknown. Here we show that forced MRTF-A expression induces CCN1 and CCN2 to promote capillary proliferation and pericyte recruitment, respectively. We demonstrate that, upon G-actin binding, thymosin 4 (T 4), induces MRTF translocation to the nucleus, SRF-activation and CCN1/2 transcription. In a murine ischaemic hindlimb model, MRTF-A or T 4 promotes neovascularization, whereas loss of MRTF-A/B or CCN1-function abrogates the T 4 effect. We further show that, in ischaemic rabbit hindlimbs, MRTF-A as well as T 4 induce functional neovascularization, and that this process is inhibited by angiopoietin-2, which antagonizes pericyte recruitment. Moreover, MRTF-A improves contractile function of chronic hibernating myocardium of pigs to a level comparable to that of transgenic pigs overexpressing T 4 (T 4tg). We conclude that MRTF-A promotes microvessel growth (via CCN1) and maturation (via CCN2), thereby enabling functional improvement of ischaemic muscle tissue.