Abstract
Caveolin-1 (CAV1) is a membrane protein that promotes migration, invasion and metastasis of cancer cells when phosphorylated on tyrosine-14 (Y14) by a cell intrinsic mechanism involving the activation of a novel Rab5-Rac1 signaling axis. Moreover, CAV1 expressed in aggressive cancer cells is included into extracellular vesicles (EVs) and such EVs increase the metastatic potential of recipient lower grade cancer cells. However, the relevance of CAV1 Y14 phosphorylation in these extrinsic EV-stimulated events remained to be determined. Here we used B16F10 mouse melanoma cells over-expressing wild-type CAV1, phospho-mimetic CAV1(Y14E) or phospho-null CAV1(Y14F) as models to determine how the EV protein content was affected by Y14 phosphorylation and how these EVs modulated the metastatic potential of recipient B16F10 cells lacking CAV1. EVs from B16F10 cells over-expressing wild-type and CAV1(Y14/E) contain CAV1, and other proteins linked to signaling pathways associated with cell adhesion and migration. CAV1 inclusion in EVs was reduced by the Y14F mutation and global protein composition was also significantly different. Moreover, CAV1 wild-type and CAV1(Y14E) EVs promoted migration, as well as invasion of cells lacking CAV1 [B16F10(Mock) cells]. In addition, β3 integrin was transferred via CAV1(Y14E) EVs to B16F10 (Mock) cells, and treatment with such EVs promoted metastasis of recipient B16F10(Mock) cells. Finally, CAV1(Y14E) EV-enhanced migration, invasion and metastasis of recipient cells was blocked by anti-αVβ3 antibodies. In conclusion, CAV1 phosphorylated on Y14 not only intrinsically promotes migration, invasion and metastasis of cells expressing the protein (in cis), but also favors the inclusion of CAV1 into EVs, as well as the extrinsic acquisition of malignant traits in recipient cells, through integrin transfer (in trans).
Keywords:
B16F10 cells; Cancer malignancy; Caveolin-1; Exosomes; Integrin transfer.