Can 4.5 Video Textures support alpha channels?

thanks Etienne Andlau my use of this is to get a chroma key in AE using keylight, in case I would use 4.18 is there any plugin to do this chroma key inside UE4? what would be the most effective way to do it? node bluescript or a tool/setting inside ue4 4.18?? what is your exp?