In this case the variable names on the input and output busses for the POU will need to be INT1, INT2, and Out2.
What you can do is don't connect the input bus and output bus from the POU to your main busses. Instead, for example, connect your input signal 'Signal1' by itself to the input bus of the POU, and then rename it on that bus as INT1. So you'll have just the green wires going to the input bus and output bus of the POU. Does that make sense?