RESUMO
OBJECTIVE: Endothelial progenitor cells (EPCs) comprise a heterogeneous population of cells, which improve therapeutic neovascularization after ischemia. The neovascularization-promoting potential of progenitor cells depends on survival and retention of the infused cells to the tissue. Caspases mediate apoptosis but are also involved in other critical biological processes. Therefore, we aimed to address the role of caspases in proangiogenic cells. METHODS AND RESULTS: The caspase-8 inhibitor zIETD abrogated the ex vivo formation of EPCs, inhibited EPC adhesion and migration, and reduced their capacity to improve neovascularization in vivo. Consistently, cells isolated from caspase-8-deficient mice exhibited a reduced capacity for enhancing neovascularization when transplanted into mice after hindlimb ischemia. Because inhibition of Caspase-8 reduced the adhesion and homing functions of EPCs, we further determined the surface expression of integrins and receptors involved in cell recruitment to ischemic tissues. Pharmacological inhibition of caspase-8 and genetic depletion of caspase-8 reduced the expression of the fibronectin receptor subunits alpha5 and beta1 and the SDF-1 receptor CXCR4. Moreover, we identified the E3 ubiquitin ligase Cbl-b, which negatively regulates integrin and receptor-mediated signaling, as a potential Caspase-8 substrate. CONCLUSIONS: In summary, our data demonstrate a novel apoptosis-unrelated role of caspase-8 in proangiogenic cells.
Assuntos
Caspase 8/metabolismo , Células Endoteliais/enzimologia , Isquemia/enzimologia , Músculo Esquelético/irrigação sanguínea , Neovascularização Fisiológica , Células-Tronco/enzimologia , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Síndrome de Alstrom , Animais , Caspase 8/genética , Inibidores de Caspase , Adesão Celular , Movimento Celular , Células Cultivadas , Inibidores de Cisteína Proteinase/farmacologia , Modelos Animais de Doenças , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/transplante , Membro Posterior , Humanos , Integrina alfaV/metabolismo , Integrina beta1/metabolismo , Isquemia/fisiopatologia , Isquemia/cirurgia , Camundongos , Camundongos Knockout , Camundongos Nus , Neovascularização Fisiológica/efeitos dos fármacos , Oligopeptídeos/farmacologia , Proteínas Proto-Oncogênicas c-cbl/metabolismo , RNA Mensageiro/metabolismo , Receptores CXCR4/metabolismo , Receptores de Fibronectina/metabolismo , Transplante de Células-Tronco , Células-Tronco/efeitos dos fármacosRESUMO
Emerging technologies are creating increasing interest in smart materials that may serve as actuators in micro- and nanodevices. Mechanically active polymers currently studied include a variety of materials. ATP-driven motor proteins, the actuators of living cells, possess promising characteristics, but their dependence on strictly defined chemical environments can be disadvantagous. Natural proteins that deform reversibly by entropic mechanisms might serve as models for artificial contractile polypeptides with useful functionality, but they are rare. Protein bodies from sieve elements of higher plants provide a novel example. sieve elements form microfluidics systems for pressure-driven transport of photo-assimilates throughout the plant. Unique protein bodies in the sieve elements of legumes act as cellular stopcocks, by undergoing a Ca2+-dependent conformational switch in which they plug the sieve element. In living cells, this reaction is probably controlled by Ca2+-transporters in the cell membrane. Here we report the rapid, reversible, anisotropic and ATP-independent contractility in these protein bodies in vitro. Considering the unique biological function of the legume 'crystalloid' protein bodies and their contractile properties, we suggest to give them the distinctive name forisome ('gate-body'; from the Latin foris, the wing of a gate).