Molecular mechanisms of CD99-induced caspase-independent cell death and cell-cell adhesion in Ewing's sarcoma cells: actin and zyxin as key intracellular mediators.
CD99 is a unique 32-kDa cell surface molecule with broad cellular expression but still poorly understood biological functions. In cancer cells, CD99 is highly expressed in virtually all Ewing's sarcoma (ES). Engagement of CD99 induces fast homotypic aggregation of ES cells and caspase-independent apoptosis. In this study, we analysed signal transduction after CD99 engagement on ES cells. Findings obtained with selective inhibitors indicated that only actin cytoskeleton integrity was essential for cell-cell adhesion and apoptosis of ES cells. Indeed, CD99 stimulation induced actin repolymerization, further supporting the role of cytoskeleton in CD99 signaling. Gene expression profiling of ES cells after CD99 engagement showed modulation in the expression of 32 genes. Among the pool of upregulated genes reported to be involved in cell adhesion, we chose to analyse the role of zyxin, a cytoplasmic adherens junction protein found to play a role in the regulation of the actin cytoskeleton. Overexpression of zyxin after CD99 ligation was confirmed by real-time PCR and Western blot. Treatment of ES cells with zyxin antisense oligonucleotides inhibited CD99-induced cell aggregation and apoptosis, suggesting a functional role for this protein. Therefore, our findings indicate that CD99 functions occur through reorganization of cytoskeleton and identify actin and zyxin as the early signaling events driven by CD99 engagement.
Cerisano
Vanessa
V
Laboratorio di Ricerca Oncologica, Istituti Ortopedici Rizzoli, Bologna 40136, Italy.
Aalto
Yan
Y
Perdichizzi
Stefania
S
Bernard
Ghislaine
G
Manara
Maria Cristina
MC
Benini
Stefania
S
Cenacchi
Giovanna
G
Preda
Paola
P
Lattanzi
Giovanna
G
Nagy
Bálint
B
Knuutila
Sakari
S
Colombo
Mario Paolo
MP
Bernard
Alain
A
Picci
Piero
P
Scotlandi
Katia
K
D000199:Actins / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002449:Cell Aggregation; D016923:Cell Death; D003598:Cytoskeletal Proteins; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D012512:Sarcoma, Ewing / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D060589:Zyxin
D000199:Actins; D003598:Cytoskeletal Proteins; D006023:Glycoproteins; C092842:ZYX protein, human; D060589:Zyxin; D020169:Caspases