Pro-adhesive and Chemotactic Activities of Thrombospondin-1 for Breast Carcinoma Cells Are Mediated by α3β1 Integrin and Regulated by Insulin-like Growth Factor-1 and CD98

Abstract

Thrombospondin-1 (TSP1) is a matricellular protein that displays both pro-and anti-adhesive activities. Binding to sulfated glycoconjugates mediates most high affinity binding of soluble TSP1 to MDA-MB-435 cells, but attachment and spreading of these cells on immobilized TSP1 is primarily ␤ 1 integrin-dependent. The integrin ␣ 3 ␤ 1 is the major mediator of breast carcinoma cell adhesion and chemotaxis to TSP1. This integrin is partially active in MDA-MB-435 cells but is mostly inactive in MDA-MB-231 and MCF-7 cells, which require ␤ 1 integrin activation to induce spreading on TSP1. Integrinmediated cell spreading on TSP1 is accompanied by extension of filopodia containing ␤ 1 integrins. TSP1 binding activity of the ␣ 3 ␤ 1 integrin is not stimulated by CD47-binding peptides from TSP1 or by protein kinase C activation, which activate ␣ v ␤ 3 integrin function in the same cells. In MDA-MB-231 but not MDA-MB-435 cells, this integrin is activated by pertussis toxin, whereas serum, insulin, insulin-like growth factor-1, and ligation of CD98 increase activity of this integrin in both cell lines. Serum stimulation is accompanied by increased surface expression of CD98, whereas insulinlike growth factor-1 does not increase CD98 expression. Thus, the pro-adhesive activity of TSP1 for breast carcinoma cells is controlled by several signals that regulate activity of the ␣ 3 ␤ 1 integrin. Thrombospondin-1 (TSP1)1 is an extracellular matrix glycoprotein that has diverse effects on cell behavior (reviewed in Refs. 1 and 2). The five known thrombospondin genes display distinct patterns of expression during development and in several disease states. Disruption of the thbs1 gene in mice results in lordosis of the spine and abnormal proliferation and inflammatory responses in the lung (3). Suppression of THBS1 expression by loss of wild type p53, by activated Ras, Myc, nickel, and in metastatic clones of several tumor cell lines suggested that loss of TSP1 expression may contribute to tumor progression (reviewed in Ref. 4). Consistent with this hypothesis, overexpression of THBS1 in breast carcinoma cells (5), a transformed endothelial cell line (6), fibroblasts from Li Fraumini patients (7), and glioblastoma cells (8) decreases tumor growth in animal models. This suppressive activity is due at least in part to the anti-angiogenic activity of TSP1 (reviewed in Refs. 4, 9, and 10). TSP1 antagonizes growth factor-stimulated proliferation and migration of endothelial cells. Its anti-angiogenic activity is thought to be the major mechanism for suppression of tumor growth in THBS1-transfected MDA-MB-435 breast carcinoma cells, because thrombospondin overexpression strongly inhibited tumor growth in vivo but did not significantly alter in vitro proliferation, motility, or the ability of the tumor cells to form colonies in soft agar (5). However, higher doses of exogenous TSP1 and some TSP1 peptides can directly inhibit proliferation of these cells in vitro (11).Defining the receptors that recognize TSP1 on endothelial and tumor cells ...

Regulation of Integrin Function by CD47 Ligands

“…Although ligation of CD47 is now known to stimulate functions of three ␤ 1 integrins, this response is not universal in that ␣ 3 ␤ 1 integrin function was not stimulated by a CD47-binding peptide (39). As previously demonstrated for ␤ 3 integrins and ␣ 2 ␤ 1 , CD47 is physically associated with ␣ 4 ␤ 1 in cells, where it regulates function of this ␤ 1 integrin.…”

Distinct Domains of CD98hc Regulate Integrins and Amino Acid Transport

“…Consequently, the integrin-CD98hc interaction may serve to polarize the localization of CD98 and, consequently, amino acid transport. Conversely, CD98hc can influence multiple integrin-dependent functions, including virus-induced cell fusion, T-cell costimulation, and cell adhesion (13,(15)(16)(17). Thus, the CD98hc-integrin association can promote integrin-mediated cell adhesion that, in turn, could serve to localize the activities of CD98hc-linked amino acid transporters.…”

“…In addition, CD98hc binds to integrin ␤ 1A cytoplasmic domains, and this interaction correlates with CODS (14). Furthermore, clustering CD98hc activates multiple integrin-dependent functions (13,15,16) and mimics ␤ 1 integrin cosignaling in T-cells (17). Thus, CD98hc physically and functionally interacts with integrin adhesion receptors.…”

“…Thus, CD98hc physically and functionally interacts with integrin adhesion receptors. Indeed, clustering of CD98hc can stimulate several classes of integrins in multiple cell types (13,15,16).…”

CD98hc (SLC3A2) regulation of skin homeostasis wanes with age

“…Expression of CD98hc in mammalian cells stimulates amino acid transport by promoting cell surface expression of the light chain (Mastroberardino et al, 1998). In addition to its role in amino acid transport, CD98hc interacts with integrins and regulates their signaling properties (Fenczik et al, 1997(Fenczik et al, , 2001Chandrasekaran et al, 1999;Zent et al, 2000;Kolesnikova et al, 2001;Merlin et al, 2001;Feral et al, 2005). Our studies and those of others have been instrumental in understanding how CD98hc physically and functionally interacts with integrins and regulates their functions in vitro (Merlin et al, 2001;Rintoul et al, 2002;Henderson et al, 2004;Feral et al, 2005Feral et al, , 2007.…”