SPARC mediates Src-induced disruption of actin cytoskeleton via inactivation of small GTPases Rho–Rac–Cdc42

Abstract

The matricellular glycoprotein Secreted Protein Acidic and Rich in Cysteine (SPARC) plays an important role in the regulation of cell adhesion and proliferation as well as in tumorigenesis and metastasis. Earlier, we reported that, in addition to its potent anti-angiogenic functions, SPARC also induces apoptosis in medulloblastoma cells, mediated by autophagy. We therefore sought to investigate the underlying molecular mechanism through which SPARC inhibits migration and invasion of Daoy medulloblastoma cells, both in vitro and in vivo. For this study, we used SPARC-overexpressing stable Daoy medulloblastoma cells. SPARC overexpression in Daoy medulloblastoma cells inhibited migration and invasion in vitro. Additionally, SPARC overexpression significantly suppressed the activity of Rho, Rac and Cdc42, which all regulate the actin cytoskeleton. This suppression was accompanied by an increase in the phosphorylation of Src at TYR-416, which led to a loss of actin stress fibers and focal contacts and a decrease in the phosphorylation level of cofilin. The reduced phosphorylation level of cofilin, which is indicative of receding Rho function, in turn led to inhibition of active Rho A. To confirm the role of SPARC in inhibition of migration and invasion of Daoy medulloblastoma cells, we transfected parental and SPARC-overexpressing Daoy cells with a plasmid vector carrying siRNA against SPARC. Transfection with SPARC siRNA reversed Src-mediated disruption of the cytoskeleton organization as well as dephosphorylation of cofilin and activation of Rho A. Taken together, these results establish SPARC as an effector of Src-induced cytoskeleton disruption in Daoy medulloblastoma cells, which subsequently led to decreased migration and invasion.

SPARC (secreted protein acidic and rich in cysteine) knockdown protects mice from acute liver injury by reducing vascular endothelial cell damage

“…In accordance with phalloidin results, we observed the increased expression of CAPZB and tropomyosin 4 ( TPM4 , NM_001001491) that stabilizes actin filaments and has a role in the regulation of cell morphology and cytoskeletal organization. This result agrees with Bhoopathi et al 20 that reports SPARC as an effector of Scr-induced cytoskeleton disruption in meduloblastoma cells. Our best Ingenuity Pathway Analysis gene network model showed that SPARC depletion was associated with an upregulation of CAPZB gene, involved in the regulation of cell morphology and cytoskeletal organization, 21 and TUBB2B , a major component of microtubules.…”

SPARC is associated with carcinogenesis of oral squamous epithelium and consistent with cell competition

“…For example, SPARC expression is correlated with malignancy, in breast cancer [10,11], melanoma [12,13], osteosarcoma [14], glioblastoma [15], and bladder cancer [16], and has a tumor-suppressing effect in medulloblastoma [17] and ovarian cancer [18,19]. In colon cancer [20], pancreatic adenocarcinoma [21,22], and nonsmall cell lung cancer [23], stromal SPARC expression is related with prognosis.…”

Integrated Analysis of Global mRNA and Protein Expression Data in HEK293 Cells Overexpressing PRL-1

“…Both molecules display similar tumor type specific influences on human tumor tissues [17], [70], [71], [79]–[82]. Both can also exert similar effects on downstream signaling pathways and molecules such as E-Cadherin [12], [83], Src [11], [84], FAK [11], [83], ERK1/2 [11], [85], MMP2 [11], [86], Akt, p53, p21 cip1/waf1 [23], [87], [88], and the Rho GTPase family members [12], [84]. Moreover, both genes have been implicated in maintenance of retinal function [5], [89], [90].…”