scholarly journals Contrasting roles for integrin beta 1 and beta 5 cytoplasmic domains in subcellular localization, cell proliferation, and cell migration.

1994 ◽  
Vol 125 (2) ◽  
pp. 447-460 ◽  
Author(s):  
R Pasqualini ◽  
M E Hemler
Keyword(s):  
Cell Proliferation ◽  
Cell Migration ◽  
Focal Adhesion ◽  
Cho Cells ◽  
Detailed Comparison ◽  
Cytoplasmic Domain ◽  
Integrin Subunit ◽  
Cytoplasmic Domains ◽  
Migration Assay ◽  
Inside Out

To carry out a detailed comparison of the roles of integrin beta 1 and beta 5 cytoplasmic domains, we expressed both wild type beta 1 and chimeric beta 1/5 constructs in CHO cells. In the latter, the cytoplasmic domain of beta 1 was replaced with that of beta 5. The human beta 1 and beta 1/5 constructs appeared at similar levels at the cell surface (mostly as alpha 5 beta 1 heterodimers) and contributed equally to CHO cell adhesion to fibronectin. However, beta 1 but not beta 1/5 localized to focal adhesion-like structures when CHO cells were spread on fibronectin. Furthermore, only the beta 1-CHO cells showed increased proliferation in response to fibronectin plus an integrin-activating anti-beta 1 antibody, and showed increased appearance of 32P-labeled protein (p90) that correlated with proliferation. In sharp contrast, the beta 1/5-CHO cells were notably more migratory than beta 1-CHO cells in a transwell haptotactic migration assay. These results indicate that the beta 1 and beta 5 integrin subunit cytoplasmic domains can translate similar adhesive information into highly contrasting subsequent events. Thus, we have established that "inside-out" and "outside-in" integrin signaling pathways are regulated by fundamentally distinct mechanisms. In addition, we suggest that the same properties of the beta 1 cytoplasmic domain that promote recruitment to visible focal adhesion-like structures may also be conductive to cell proliferation. Conversely, the properties of the beta 5 tail that make it less likely to localize into focal adhesion-like structures may contribute to enhanced cell migration.

scholarly journals Specialized functional properties of the integrin alpha 4 cytoplasmic domain.

1995 ◽  
Vol 6 (6) ◽  
pp. 661-674 ◽  
Author(s):  
P D Kassner ◽  
R Alon ◽  
T A Springer ◽  
M E Hemler
Keyword(s):  
Cell Migration ◽  
Shear Flow ◽  
Focal Adhesion ◽  
Cho Cells ◽  
Adhesion Formation ◽  
Chinese Hamster ◽  
Focal Adhesions ◽  
Cell Spreading ◽  
Cytoplasmic Domain ◽  
Positive Effects

For functional studies of the integrin alpha 4 cytoplasmic domain, we have expressed the following in K562 and Chinese hamster ovary (CHO) cells: 1) wild-type alpha 4 (called X4C4), 2) two chimeric forms of alpha 4 (called X4C2 and X4C5) that contain the cytoplasmic domains of alpha 2 and alpha 5, respectively, and 3) alpha 4 with no cytoplasmic domain (X4C0). Cytoplasmic domain exchange had no effect on VLA-4-dependent static cell adhesion or tethering to VCAM-1 in conditions of shear flow. However, the presence of the alpha 2 or alpha 5 tails markedly enhanced VLA-4-dependent K562 cells spreading (X4C2 > X4C5 > X4C4 > X4C0), increased localization of VLA-4 into focal adhesion-like complexes in CHO cells (X4C2 > X4C5 > X4C4), and strengthened CHO and K562 cell resistance to detachment from VCAM-1 in conditions of shear flow (X4C2 > X4C5 > X4C4 > X4C0). Conversely, the alpha 4 tail supported greater VLA-4-dependent haptotactic and chemotactic cell migration. In the absence of any alpha tail (i.e., X4C0), robust focal adhesions were observed, even though cell spreading and adhesion strengthening were minimal. Thus, such focal adhesions may have relatively little functional importance, and should not be compared with focal adhesions formed when alpha tails are present. Together, these results indicate that all three alpha-chain tails exert defined positive effects (compared with no tail at all), but suggest that the alpha 4 cytoplasmic domain may be specialized to engage in weaker cytoskeletal interactions, leading to diminished focal adhesion formation, cell spreading, and adhesion strengthening, while augmenting cell migration and facilitating rolling under shear flow. These properties of the alpha 4 tail are consistent with the role of alpha 4 integrins on highly motile lymphocytes, monocytes, and eosinophils.

scholarly journals Integrin cytoplasmic domains mediate inside-out signal transduction

1994 ◽  
Vol 124 (6) ◽  
pp. 1047-1059 ◽  
Author(s):  
TE O'Toole ◽  
Y Katagiri ◽  
RJ Faull ◽  
K Peter ◽  
R Tamura ◽  
...  
Keyword(s):  
K562 Cells ◽  
Cytoplasmic Domain ◽  
Alpha Subunit ◽  
Affinity Binding ◽  
Cell Type ◽  
Cytoplasmic Domains ◽  
High Affinity Binding ◽  
High Affinity ◽  
Energy Dependent ◽  
Inside Out

We analyzed the binding of fibronectin to integrin alpha 5 beta 1 in various cells; in some cells fibronectin bound with low affinity (e.g., K562 cells) whereas in others (e.g., CHO), it bound with high affinity (Kd approximately 100 nM) in an energy-dependent manner. We constructed chimeras of the extracellular and transmembrane domains of alpha IIb beta 3 joined to the cytoplasmic domains of alpha 5 beta 1. The affinity state of these chimeras was assessed by binding of fibrinogen or the monoclonal antibody, PAC1. The cytoplasmic domains of alpha 5 beta 1 conferred an energy-dependent high affinity state on alpha IIb beta 3 in CHO but not K562 cells. Three additional alpha cytoplasmic domains (alpha 2, alpha 6A, alpha 6B) conferred PAC1 binding in CHO cells, while three others (alpha M, alpha L, alpha v) did not. In the high affinity alpha chimeras, cotransfection with a truncated (beta 3 delta 724) or mutated (beta 3(S752-->P)) beta 3 subunit abolished high affinity binding. Thus, both cytoplasmic domains are required for energy-dependent, cell type-specific affinity modulation. In addition, mutations that disrupted a highly conserved alpha subunit GFFKR motif, resulted in high affinity binding of ligands to alpha IIb beta 3. In contrast to the chimeras, the high affinity state of these mutants was independent of cellular metabolism, cell type, and the bulk of the beta subunit cytoplasmic domain. Thus, integrin cytoplasmic domains mediate inside-out signaling. Furthermore, the highly conserved GFFKR motif of the alpha subunit cytoplasmic domain maintains the default low affinity state.

scholarly journals Integrin alpha 2 cytoplasmic domain deletion effects: loss of adhesive activity parallels ligand-independent recruitment into focal adhesions.

1994 ◽  
Vol 5 (9) ◽  
pp. 977-988 ◽  
Author(s):  
S Kawaguchi ◽  
J M Bergelson ◽  
R W Finberg ◽  
M E Hemler
Keyword(s):  
Amino Acids ◽  
Cell Adhesion ◽  
Focal Adhesion ◽  
Cho Cells ◽  
Chinese Hamster ◽  
Focal Adhesions ◽  
Inverse Correlation ◽  
Cytoplasmic Domain ◽  
Negative Regulator ◽  
Wild Type

Chinese hamster ovary (CHO) cells transfected with the integrin alpha 2 subunit formed a stable VLA-2 heterodimer that mediated cell adhesion to collagen. Within CHO cells spread on collagen, but not fibronectin, wild-type alpha 2 subunit localized into focal adhesion complexes (FACs). In contrast, alpha 2 with a deleted cytoplasmic domain was recruited into FACs whether CHO cells were spread on collagen or fibronectin. Thus, as previously seen for other integrins, the alpha 2 cytoplasmic domain acts as a negative regulator, preventing indiscriminate integrin recruitment into FACs. Notably, ligand-independent localization of the VLA-2 alpha 2 subunit into FACs was partially prevented if only one or two amino acids were present in the alpha 2 cytoplasmic domain (beyond the conserved GFFKR motif) and was completely prevented by four to seven amino acids. The addition of two alanine residues (added to GFFKR) also partially prevented ligand-independent localization. In a striking inverse correlation, the same mutants showing increased ligand-independent recruitment into FACs exhibited diminished alpha 2-dependent adhesion to collagen. Thus, control of VLA-2 localization may be closely related to the suppression of cell adhesion to collagen. In contrast to FAC localization and collagen adhesion results, VLA-2-dependent binding and infection by echovirus were unaffected by either alpha 2 cytoplasmic domain deletion or exchange with other cytoplasmic domains.

scholarly journals Long noncoding RNA LSINCT5 promotes endometrial carcinoma cell proliferation, cycle, and invasion by promoting the Wnt/β-catenin signaling pathway via HMGA2

2019 ◽  
Vol 11 ◽  
pp. 175883591987464 ◽  
Author(s):  
Hongye Jiang ◽  
Yong Li ◽  
Jie Li ◽  
Xuyu Zhang ◽  
Gang Niu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Migration ◽  
Endometrial Carcinoma ◽  
Signaling Pathway ◽  
Long Noncoding Rna ◽  
Noncoding Rna ◽  
Critical Role ◽  
Migration And Invasion ◽  
Migration Assay

Background: A review of the evidence has indicated the critical role of long noncoding RNA (lncRNA) LSINCT5 in a large number of human cancers. However, the mechanistic involvement of LSINCT5 in endometrial carcinoma (EC) is still unknown. Here the authors aim to characterize the expression status of LSINCT5 and elucidate its mechanistic relevance to EC. Methods: Relative expression of LSINCT5 and HMGA2 were quantified by a real-time polymerase chain reaction. SiRNAs were employed to specifically knockdown endogenous LSINCT5 in EC cells. Cell proliferation was measured with Cell Count Kit-8 kit (CCK-8, Dojindo, Kumamoto, Japan) and cell growth was assessed by a colony formation assay. The cell cycle was analyzed with propidium iodide (PI) staining. Apoptotic cells were determined by flow cytometry after Annexin V/PI double-staining. Cell migration was evaluated by a wound-healing assay, and cell invasion was assessed using a transwell migration assay. The protein levels of HMGA2, Wnt3a, p-β-catenin, c-myc, β-actin, and GAPDH were determined by western blot. Results: The authors observed positively correlated and aberrantly up-regulated LSINCT5 and HMGA2 in EC. LSINCT5 deficiency significantly inhibited cell proliferation, cell cycle progression, and induced apoptosis. Meanwhile, cell migration and invasion were greatly compromised by the LSINCT5 knockdown. LSINCT5 stabilized HMGA2, which subsequently stimulated activation of Wnt/β-catenin signaling and consequently contributed to the oncogenic properties of LSINCT5 in EC. Conclusions: Our data uncovered the oncogenic activities and highlighted the mechanistic contributions of the LSINCT5-HMGA2-Wnt/β-catenin signaling pathway in EC.

VPS33B, a Member of the Sec1/Munc18 Protein Family, Binds to Integrin Beta Subunits and Is Required for αIIbβ3 Outside-in Signaling

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 340-340
Author(s):  
Binggang Xiang ◽  
Guoying Zhang ◽  
Shaojing Ye ◽  
Cai Huang ◽  
Jun Liu ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Cho Cells ◽  
Human Platelet ◽  
Cell Spreading ◽  
Cytoplasmic Domain ◽  
Integrin Activation ◽  
Clot Retraction ◽  
Domain Fusion ◽  
Inside Out

Abstract Integrins play fundamental roles in many biological processes such as development, immunity, cancer, wound healing, hemostasis, and thrombosis. Integrin activation is essential for cell adhesion, spreading, survival, proliferation, and migration. Integrins are heterodimeric transmembrane glycoproteins composed of a and b subunits. The function of integrins is modulated by bi-directional transmembrane signaling: inside-out and outside-in signaling, which are mediated through the interactions between integrin a or b subunit cytoplasmic tails and intracellular proteins and can be regulated by many different biochemical signaling pathways. αIIbβ3 is a major integrin expressed in megakaryocytes and platelets. Antagonists of αIIbβ3 are potent anti-thrombotic drugs and new inhibitors targeting αIIbβ3 are under preclinical testing or large patient trials to treat acute coronary syndromes. Integrin αIIbβ3 activation involves binding of proteins, including talin, kindlins, Src kinase, and Gα13 to the cytoplasmic domain of its β subunit. To gain insight into αIIbβ3signaling and to identify new proteins that regulate αIIbβ3 activation, agarose beads conjugated with glutathione S-transferase (GST)-β3 integrin cytoplasmic domain fusion protein (GST-β3CD) or GST-αIIb integrin cytoplasmic domain fusion protein (GST-αIIbCD) were incubated with human platelet lysates. Proteins pulled down by the GST-β3CD or GST-αIIbCD beads were subjected to mass spectrometric analysis. We found that the GST-β3CD but not the GST-αIIbCD beads specifically pulled down a previously unreported protein, the vacuolar protein sorting-associated protein 33B (VPS33B), encoded by the VPS33B gene. To verify that VPS33B is in a complex with αIIbβ3, we infected Chinese hamster ovary (CHO) cells stably expressing αIIbβ3 (A5 cells) with an adenovirus containing FLAG epitope-tagged human VPS33B cDNA. Cells were allowed to adhere and spread on fibrinogen. FLAG-VPS33B exhibited a significant intracellular colocalization with aIIbb3. Immunoblotting analysis revealed a specific association of b3 with precipitated FLAG-VPS33B. The specific interaction was also confirmed by reciprocal immunoprecipitation using a specific β3antibody. Furthermore, in an in vitro binding assay, we were able to pull down VPS33B from the lysates of CHO cells overexpressing VPS33B by the GST-β3CD beads. The interaction appears to be direct, since we were also able to pull down purified FLAG-VPS33B with GST-β3CD and GST-β1CD proteins. The pulldown assay showed that the β3 fragment spanning residues 716~730 bound efficiently to FLAG-VPS33B. In contrast, the fragments containing either residues 729~762 or residues 744~762 fragments failed to do the same. More importantly, using the rabbit polyclonal antibody against VPS33B, we were able to coimmunoprecipitate endogenous b3 subunit with VPS33B from human platelet lysate. Thus, we identified a novel binding protein of integrin β3. Next, we investigated the role of VPS33B in integrin activation using a recombinant integrin activation model of CHO cells. Overexpression of VPS33B in CHO cells expressing αIIbβ3 (A5 cells) markedly potentiated cell spreading on fibrinogen and F-actin formation. To establish a role of VPS33B in integrin activation in platelets, we created a mouse model with megakaryocyte- and platelet-specific deletion of VPS33B. Platelets lacking VPS33B were defective in spreading on fibrinogen. VPS33B-/- platelets failed to support clot retraction. On the other hand, thrombin-induced fibrinogen binding to platelets and platelet aggregation were not affected by the loss of VPS33B. Collectively, these results demonstrate an essential role of VPS33B in αIIbβ3 outside-in signaling but is not requried for integrin inside-out signaling. We further demonstrate that VPS33B promotes αIIbβ3 outside-in signaling through RhoA and Rac1 activation, leading to clot retraction and cell spreading, respectively. Therefore, our results for the first time establish vesicle trafficking proteins as an important novel class of modifiers of integrin function in platelets and cells. Disclosures No relevant conflicts of interest to declare.

α1 Integrin cytoplasmic domain is involved in focal adhesion formation via association with intracellular proteins

2001 ◽  
Vol 356 (1) ◽  
pp. 233-240 ◽  
Author(s):  
Klemens LÖSTER ◽  
Dörte VOSSMEYER ◽  
Werner HOFMANN ◽  
Werner REUTTER ◽  
Kerstin DANKER
Keyword(s):  
Signal Transduction ◽  
Focal Adhesion ◽  
Protein Interactions ◽  
Adhesion Formation ◽  
Focal Adhesions ◽  
Cell Types ◽  
Cytoplasmic Domain ◽  
Integrin Subunit ◽  
Adhesion Receptors ◽  
Focal Adhesion Formation

Integrins are heterodimeric adhesion receptors consisting of α- and β-subunits capable of binding extracellular matrix molecules as well as other adhesion receptors on neighbouring cells. These interactions induce various signal transduction pathways in many cell types, leading to cytoskeletal reorganization, phosphorylation and induction of gene expression. Integrin ligation leads to cytoplasmic protein–protein interactions requiring both integrin cytoplasmic domains, and these domains are initiation points for focal adhesion formation and subsequent signal transduction cascades. In previous studies we have shown that the very short cytoplasmic α1 tail is required for post-ligand events, such as cell spreading as well as actin stress-fibre formation. In the present paper we report that cells lacking the cytoplasmic domain of the α1 integrin subunit are unable to form proper focal adhesions and that phosphorylation on tyrosine residues of focal adhesion components is reduced on α1β1-specific substrates. The α1 cytoplasmic sequence is a specific recognition site for focal adhesion components like paxillin, talin, α-actinin and pp125FAK. It seems to account for α1-specific signalling, since when peptides that mimic the cytoplasmic domain of α1 are transferred into cells, they influence α1β1-specific adhesion, presumably by competing for binding partners. For α1 integrin/protein binding, the conserved Lys-Ile-Gly-Phe-Phe-Lys-Arg motif and, in particular, the two lysine residues, are important.

scholarly journals Dominant-negative effect on adhesion by myelin Po protein truncated in its cytoplasmic domain.

1996 ◽  
Vol 134 (6) ◽  
pp. 1531-1541 ◽  
Author(s):  
M H Wong ◽  
M T Filbin
Keyword(s):  
Cho Cells ◽  
Cytoplasmic Domain ◽  
Dominant Negative ◽  
Full Length ◽  
Dominant Negative Effect ◽  
Cytoplasmic Domains ◽  
Aggregation Assay ◽  
Negative Effect ◽  
Po Protein ◽  
Homophilic Adhesion

The myelin Po protein is believed to hold myelin together via interactions of both its extracellular and cytoplasmic domains. We have already shown that the extracellular domains of Po can interact in a homophilic manner (Filbin, M.T., F.S. Walsh, B.D. Trapp, J.A. Pizzey, and G.I. Tennekoon. 1990. Nature (Lond.). 344:871-872). In addition, we have shown that for this homophilic adhesion to take place, the cytoplasmic domain of Po must be intact and most likely interacting with the cytoskeleton; Po proteins truncated in their cytoplasmic domains are not adhesive (Wong, M.H., and M.T. Filbin, 1994. J. Cell Biol. 126:1089-1097). To determine if the presence of these truncated forms of Po could have an effect on the functioning of the full-length Po, we coexpressed both molecules in CHO cells. The adhesiveness of CHO cells expressing both full-length Po and truncated Po was then compared to cells expressing only full-length Po. In these coexpressors, both the full-length and the truncated Po proteins were glycosylated. They reached the surface of the cell in approximately equal amounts as shown by an ELISA and surface labeling, followed by immunoprecipitation. Furthermore, the amount of full-length Po at the cell surface was equivalent to other cell lines expressing only full-length Po that we had already shown to be adhesive. Therefore, there should be sufficient levels of full-length Po at the surface of these coexpressors to measure adhesion of Po. However, as assessed by an aggregation assay, the coexpressors were not adhesive. By 60 min they had not formed large aggregates and were indistinguishable from the control transfected cells not expressing Po. In contrast, in the same time, the cells expressing only the full-length Po had formed large aggregates. This indicates that the truncated forms of Po have a dominant-negative effect on the adhesiveness of the full-length Po. Furthermore, from cross-linking studies, full-length Po, when expressed alone but not when coexpressed with truncated Po, appears to cluster in the membrane. We suggest that truncated Po exerts its dominant-negative effect by preventing clustering of full-length Po. We also show that colchicine, which disrupts microtubules, prevents adhesion of cells expressing only the full-length Po. This strengthens our suggestion that an interaction of Po with the cytoskeleton, either directly or indirectly, is required for adhesion to take place.

scholarly journals Quantitative Changes in Integrin and Focal Adhesion Signaling Regulate Myoblast Cell Cycle Withdrawal

1999 ◽  
Vol 144 (6) ◽  
pp. 1295-1309 ◽  
Author(s):  
Sarita K. Sastry ◽  
Margot Lakonishok ◽  
Stanley Wu ◽  
Tho Q. Truong ◽  
Anna Huttenlocher ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Map Kinase ◽  
Focal Adhesion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Cytoplasmic Domain ◽  
Cytoplasmic Domains ◽  
Α Subunit ◽  
Kinase Activation ◽  
Quantitative Changes

We previously demonstrated contrasting roles for integrin α subunits and their cytoplasmic domains in controlling cell cycle withdrawal and the onset of terminal differentiation (Sastry, S., M. Lakonishok, D. Thomas, J. Muschler, and A.F. Horwitz. 1996. J. Cell Biol. 133:169–184). Ectopic expression of the integrin α5 or α6A subunit in primary quail myoblasts either decreases or enhances the probability of cell cycle withdrawal, respectively. In this study, we addressed the mechanisms by which changes in integrin α subunit ratios regulate this decision. Ectopic expression of truncated α5 or α6A indicate that the α5 cytoplasmic domain is permissive for the proliferative pathway whereas the COOH-terminal 11 amino acids of α6A cytoplasmic domain inhibit proliferation and promote differentiation. The α5 and α6A cytoplasmic domains do not appear to initiate these signals directly, but instead regulate β1 signaling. Ectopically expressed IL2R-α5 or IL2R-α6A have no detectable effect on the myoblast phenotype. However, ectopic expression of the β1A integrin subunit or IL2R-β1A, autonomously inhibits differentiation and maintains a proliferative state. Perturbing α5 or α6A ratios also significantly affects activation of β1 integrin signaling pathways. Ectopic α5 expression enhances expression and activation of paxillin as well as mitogen-activated protein (MAP) kinase with little effect on focal adhesion kinase (FAK). In contrast, ectopic α6A expression suppresses FAK and MAP kinase activation with a lesser effect on paxillin. Ectopic expression of wild-type and mutant forms of FAK, paxillin, and MAP/erk kinase (MEK) confirm these correlations. These data demonstrate that (a) proliferative signaling (i.e., inhibition of cell cycle withdrawal and the onset of terminal differentiation) occurs through the β1A subunit and is modulated by the α subunit cytoplasmic domains; (b) perturbing α subunit ratios alters paxillin expression and phosphorylation and FAK and MAP kinase activation; (c) quantitative changes in the level of adhesive signaling through integrins and focal adhesion components regulate the decision of myoblasts to withdraw from the cell cycle, in part via MAP kinase.

scholarly journals Integrin α9 Suppresses Hepatocellular Carcinoma Metastasis by Rho GTPase Signaling

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yan-Li Zhang ◽  
Xin Xing ◽  
Li-Bo Cai ◽  
Lei Zhu ◽  
Xiao-Mei Yang ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Migration ◽  
Focal Adhesion ◽  
Molecular Mechanisms ◽  
Rho Gtpase ◽  
Migration And Invasion ◽  
Integrin Subunit ◽  
Src Tyrosine Kinase ◽  
Tumor Cell Migration

Integrin subunit alpha 9 (ITGA9) mediates cell-cell and cell-matrix adhesion, cell migration, and invasion through binding different kinds of extracellular matrix (ECM) components. However, its potential role and underlying molecular mechanisms remain unclear in hepatocellular carcinoma (HCC). Here, we found that ITGA9 expression was obviously decreased in patients with HCC, which was negatively correlated with HCC growth and metastasis. ITGA9 overexpression significantly inhibited cell proliferation and migration in vitro as well as tumor growth and metastasis in vivo. Our data demonstrated that the inhibitory effect of ITGA9 on HCC cell motility was associated with reduced phosphorylation of focal adhesion kinase (FAK) and c-Src tyrosine kinase (Src), disrupted focal adhesion reorganization, and decreased Rac1 and RhoA activity. Our data suggest ITGA9, as a suppressor of HCC, prevents tumor cell migration and invasiveness through FAK/Src-Rac1/RhoA signaling.

scholarly journals The Cytoplasmic Domain of the Integrin α9 Subunit Requires the Adaptor Protein Paxillin to Inhibit Cell Spreading but Promotes Cell Migration in a Paxillin-independent Manner

2001 ◽  
Vol 12 (10) ◽  
pp. 3214-3225 ◽  
Author(s):  
Bradford A. Young ◽  
Yasuyuki Taooka ◽  
Shouchun Liu ◽  
Karen J. Askins ◽  
Yasuyuki Yokosaki ◽  
...  
Keyword(s):  
Cell Migration ◽  
Intracellular Signaling ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Adaptor Protein ◽  
Cell Spreading ◽  
Cytoplasmic Domain ◽  
Cytoplasmic Domains ◽  
Independent Manner ◽  
Ovary Cells

The integrin α9 subunit forms a single heterodimer, α9β1. The α9 subunit is most closely related to the α4 subunit, and like α4 integrins, α9β1 plays an important role in leukocyte migration. The α4 cytoplasmic domain preferentially enhances cell migration and inhibits cell spreading, effects that depend on interaction with the adaptor protein, paxillin. To determine whether the α9 cytoplasmic domain has similar effects, a series of chimeric and deleted α9 constructs were expressed in Chinese hamster ovary cells and tested for their effects on migration and spreading on an α9β1-specific ligand. Like α4, the α9 cytoplasmic domain enhanced cell migration and inhibited cell spreading. Paxillin also specifically bound the α9 cytoplasmic domain and to a similar level as α4. In paxillin −/− cells, α9 failed to inhibit cell spreading as expected but surprisingly still enhanced cell migration. Further, mutations that abolished the α9-paxillin interaction prevented α9 from inhibiting cell spreading but had no effect on α9-dependent cell migration. These findings suggest that the mechanisms by which the cytoplasmic domains of integrin α subunits enhance migration and inhibit cell spreading are distinct and that the α9 and α4 cytoplasmic domains, despite sequence and functional similarities, enhance cell migration by different intracellular signaling pathways.

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