Tell us more about the 0-1v signal. Is the 0v- +1v signal a true digital signal, i.e. it can only be at 0v or +1v, never anything in between those two voltage levels? If so it's a digital signal and only needs to be amplified with a transistor or op-amp with a gain of 5. If however it's a true analog voltage (value may be anywhere between 0- +1vdc) then you need either a comparitor IC or an op-amp wired as a compator. It will need to have a reference set to 1/2 the input range (+1/2vde) and some kind of hystersis to make the switching point jitter free. The interrupt pin input for an Arduino is a TTL level digital input and the signal to it must be well behaved or you will either miss or have multipule interrupts in error.
Lefty