The Actin-binding Protein Caldesmon Is in Spleen and Lymph Nodes Predominately Expressed by Smooth-muscle Cells, Reticular Cells, and Follicular Dendritic Cells

Rationale: Single nucleotide polymorphism (SNP) in the LGASL2 galectin-2 (Gal-2) gene leads to altered secretion of lymphotoxin-α (LT-α) and is associated with coronary artery disease. Objective:Our aim was to determine whether factors other than genetic variations in LGASL2 regulate LT-α release and to define the role of this pro-inflammatory in vascular smooth muscle cells (SMC). Methods and results: The proinflammatory cytokine lymphotoxin-alpha (LTA) is thought to contribute to the pathogenesis of atherosclerosis. However, the mechanisms that regulate its expression in VSMC are poorly understood. The ability of exogenous nucleotides to stimulate LTA production was evaluated in VSMC by ELISA. The P2Y 2 nucleotide receptor (P2Y 2 R) agonist UTP stimulates a strong and sustained release of LTA from wild-type but not P2Y 2 R -/- SMC. Assessment of LTA gene transcription by LTA promoter-luciferase construct indicated that LTA levels are controlled at the level of transcription. We show using RNAi techniques that knockdown of the actin-binding protein filamin-A (FLNa) severely impaired nucleotide-induced Rho activation and consequent Rho-mediated LTA secretion. Re-introduction of FLNa in FLNa RNAi SMC rescued UTP-induced LTA expression. In addition, we found UTP-stimulated LTA secretion is not sensitive to brefeldin A (BFA), which blocks the formation of vesicles involved in protein transport from the ER to the Golgi apparatus, suggesting that P2Y 2 R/filamin-mediated secretion of LTA is independent of the ER/Golgi secretory vesicle route. Furthermore, UTP selectively induces ICAM-1 expression in WT but not SMC expressing a truncated P2Y 2 R deficient in LTA secretion. Conclusion: These data suggest that P2Y 2 R recruits FLNa to provide a cytoskeletal scaffold necessary for Rho signaling pathway upstream of LTA release and subsequent stimulation of ICAM-1 expression on VSMC.

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Transgelin-1 (SM22α) interacts with actin stress fibers and podosomes in smooth muscle cells without using its actin binding site

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2018.09.176 ◽

2018 ◽

Vol 505 (3) ◽

pp. 879-884 ◽

Cited By ~ 9

Author(s):

Tsubasa S. Matsui ◽

Akihiro Ishikawa ◽

Shinji Deguchi

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Binding Site ◽

Muscle Cells ◽

Stress Fibers ◽

Actin Binding ◽

Actin Binding Site ◽

Actin Stress Fibers

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Cyclic AMP-Rap1A signaling mediates cell surface translocation of microvascular smooth muscle α2C-adrenoceptors through the actin-binding protein filamin-2

AJP Cell Physiology ◽

10.1152/ajpcell.00221.2012 ◽

2013 ◽

Vol 305 (8) ◽

pp. C829-C845 ◽

Cited By ~ 22

Author(s):

Hanaa K. B. Motawea ◽

Selvi C. Jeyaraj ◽

Ali H. Eid ◽

Srabani Mitra ◽

Nicholas T. Unger ◽

...

Keyword(s):

Smooth Muscle ◽

Plasma Membrane ◽

Cyclic Amp ◽

Cell Surface ◽

Smooth Muscle Cells ◽

Blood Vessels ◽

Muscle Cells ◽

Small Gtpase ◽

Actin Binding ◽

Surface Translocation

The second messenger cyclic AMP (cAMP) plays a vital role in vascular physiology, including vasodilation of large blood vessels. We recently demonstrated cAMP activation of Epac-Rap1A and RhoA-Rho-associated kinase (ROCK)-F-actin signaling in arteriolar-derived smooth muscle cells increases expression and cell surface translocation of functional α2C-adrenoceptors (α2C-ARs) that mediate vasoconstriction in small blood vessels (arterioles). The Ras-related small GTPAse Rap1A increased expression of α2C-ARs and also increased translocation of perinuclear α2C-ARs to intracellular F-actin and to the plasma membrane. This study examined the mechanism of translocation to better understand the role of these newly discovered mediators of blood flow control, potentially activated in peripheral vascular disorders. We utilized a yeast two-hybrid screen with human microvascular smooth muscle cells (microVSM) cDNA library and the α2C-AR COOH terminus to identify a novel interaction with the actin cross-linker filamin-2. Yeast α-galactosidase assays, site-directed mutagenesis, and coimmunoprecipitation experiments in heterologous human embryonic kidney (HEK) 293 cells and in human microVSM demonstrated that α2C-ARs, but not α2A-AR subtype, interacted with filamin. In Rap1-stimulated human microVSM, α2C-ARs colocalized with filamin on intracellular filaments and at the plasma membrane. Small interfering RNA-mediated knockdown of filamin-2 inhibited Rap1-induced redistribution of α2C-ARs to the cell surface and inhibited receptor function. The studies suggest that cAMP-Rap1-Rho-ROCK signaling facilitates receptor translocation and function via phosphorylation of filamin-2 Ser2113. Together, these studies extend our previous findings to show that functional rescue of α2C-ARs is mediated through Rap1-filamin signaling. Perturbation of this signaling pathway may lead to alterations in α2C-AR trafficking and physiological function.

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Directing Traffic in Lymph Nodes

Microscopy Today ◽

10.1017/s1551929500061150 ◽

2007 ◽

Vol 15 (5) ◽

pp. 3-5

Author(s):

Stephen W. Carmichael ◽

Ellen D. Remstein

Keyword(s):

Bone Marrow ◽

T Cells ◽

Dendritic Cells ◽

Lymph Nodes ◽

B Cell ◽

Stromal Cells ◽

Follicular Dendritic Cells ◽

Adjacent Region ◽

Reticular Cells ◽

The Right

How do the right cells get to the right place in lymph nodes? It is known that lymphocytes known as B cells (that originate in the bone marrow) migrate to follicles within the nodes, whereas T cells (that originate in the bone marrow and migrate to the thymus gland) reside in an adjacent region known as the paracortex. By combining confocal, electron, and intravital microscopy, Marc Bajénoff, Jackson Egen, Lily Koo, Jean Pierre Laugier, Frédéric Brau, Nicolas Glaichenhaus, and Ronald Germain have demonstrated a role for the stroma of the node in directing these cells to the appropriate location. The stromal cells that are critical in the B cell follicles are follicular dendritic cells (FDCs) and in the paracortex it's the fibroblastic reticular cells (FRCs).

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Arp5 is a key regulator of myocardin in smooth muscle cells

The Journal of Cell Biology ◽

10.1083/jcb.201307158 ◽

2014 ◽

Vol 204 (5) ◽

pp. 683-696 ◽

Cited By ~ 10

Author(s):

Tsuyoshi Morita ◽

Ken’ichiro Hayashi

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Messenger Rna ◽

Serum Response Factor ◽

Muscle Cells ◽

Actin Binding ◽

Promoter Regions ◽

Muscle Genes ◽

Well Differentiated ◽

Serum Response

Myocardin (Myocd) and Myocd-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). RPEL motifs are monomeric globular actin (G-actin) binding elements that regulate MRTF localization and activity. However, the function of the RPEL motif in Myocd is largely unknown because of its low affinity for G-actin. Here, we demonstrated that the Myocd RPEL motif bound to actin-related protein 5 (Arp5) instead of conventional actin, resulting in a significant suppression of Myocd activity. In addition, Arp5 bound to a DNA binding domain of SRF via its C-terminal sequence and prevented the association of the Myocd–SRF complex with the promoter regions of smooth muscle genes. Well-differentiated smooth muscle cells mainly expressed a specific splicing variant of arp5; therefore, the protein level of Arp5 was markedly reduced by partial messenger RNA decay and translational suppression. In dedifferentiated smooth muscle cells, Arp5 knockdown restored the differentiated phenotype via Myocd activation. Thus, Arp5 is a key regulator of Myocd activity.

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Smoothelin, a novel cytoskeletal protein specific for smooth muscle cells.

The Journal of Cell Biology ◽

10.1083/jcb.134.2.401 ◽

1996 ◽

Vol 134 (2) ◽

pp. 401-411 ◽

Cited By ~ 164

Author(s):

F T van der Loop ◽

G Schaart ◽

E D Timmer ◽

F C Ramaekers ◽

G J van Eys

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Immunohistochemical Analysis ◽

Muscle Cells ◽

Northern Blotting ◽

Actin Binding ◽

Cytoskeletal Protein ◽

Computer Assisted ◽

Cell Fractionation ◽

Smooth Muscle Tissue

The characterization of a novel 59-kD cytoskeletal protein is described. It is exclusively observed in smooth muscle cells by Northern blotting and immunohistochemical analysis and therefore designated "smoothelin." A human smooth muscle cDNA library was screened with the monoclonal antibody R4A, and a full-size cDNA of the protein was selected. The cDNA was sequenced and appeared to contain a 1,113-bp open reading frame. Based on the cDNA sequence, the calculated molecular weight of the polypeptide was 40 kD and it was demonstrated to contain two N-glycosylation sites. Computer assisted analysis at the protein level revealed a 56-amino acid domain with homologies of approximately 40% with a sequence bordering the actin-binding domains of dystrophin, utrophin, beta-spectrin and alpha-actinin. In situ hybridization demonstrated that human smoothelin is encoded by a single copy gene which is located on chromosome 22. Immunohistochemistry and Western blotting revealed synthesis of smoothelin in smooth muscle of species evolutionarily as far apart as human and teleost. Northern blotting indicated that sequence as well as size of the mRNA (approximately 1,500 bases) are conserved among vertebrates. Cell fractionation studies and differential centrifugation showed that the protein cannot be extracted with Triton X-100, which indicates that it is a part of the cytoskeleton. Transfection of the human cDNA into smooth muscle cells and COS7 cells produced a protein of 59 kD, which assembled into a filamentous network. However, in rat heart-derived myoblasts association with stress fibers was most prominent. Smoothelin was not detected in primary or long term smooth muscle cell cultures. Also, transcription of smoothelin mRNA was almost instantly halted in smooth muscle tissue explants. We conclude that smoothelin is a new cytoskeletal protein that is only found in contractile smooth muscle cells and does not belong to one of the classes of structural proteins presently known.

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Smooth muscle cells, dendritic cells and mast cells are sources of TNFalpha and nitric oxide in human carotid artery atherosclerosis

Thrombosis Research ◽

10.1016/j.thromres.2008.04.013 ◽

2008 ◽

Vol 122 (5) ◽

pp. 657-667 ◽

Cited By ~ 16

Author(s):

Stefano Bacci ◽

Laura Pieri ◽

Anna Maria Buccoliero ◽

Aurelio Bonelli ◽

Gianluigi Taddei ◽

...

Keyword(s):

Nitric Oxide ◽

Dendritic Cells ◽

Smooth Muscle ◽

Mast Cells ◽

Carotid Artery ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Carotid Artery Atherosclerosis ◽

Human Carotid

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A rare lesion of cervical lymph nodes: Angiomyomatous hamartoma

Medical Science and Discovery ◽

10.36472/msd.v8i3.487 ◽

2021 ◽

Vol 8 (3) ◽

pp. 187-188

Author(s):

Mecdi Gurhan Balci ◽

Mahir Tayfur

Keyword(s):

Smooth Muscle ◽

Lymph Node ◽

Lymph Nodes ◽

Smooth Muscle Cells ◽

Histopathological Examination ◽

Muscle Cells ◽

Cervical Region ◽

Pathology Laboratory ◽

Cervical Lymph Nodes ◽

Vascular Structures

Objective: Angiomyomatous hamartomas are extremely rare, tumor-like lesions of the lymph nodes. They are usually seen in the inguinal region lymph nodes. They are rarely seen in the lymph nodes of the cervical region. Histopathologically, fibrous tissues, smooth muscle cells, and vascular structures are seen in the lymph node structure. It is important to distinguish it from benign and malignant lesions of the lymph node. Case: A 1 cm diameter lymph node excision material removed from the cervical region of a 26-year-old male patient was sent to the pathology laboratory with a pre-diagnosis of lymphadenitis. 4- micron sections were taken from the paraffin blocks prepared from the tissues belonging to the lesion. The samples were examined by staining Hematoxylin-Eosin. In histopathological examination, it was found that almost all of the lymph node structure consisted of vascular structures and smooth muscle cells located on a fibrous ground. The case was reported as angiomyomatous hamartoma. Conclusion: Angiomyomatous hamartomas are extremely rare lesions of the cervical lymph nodes and their consideration in differential diagnosis will reduce the risk of possible diagnostic error.

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