How to lower current consumption in JN5148-J01 Microcontroller?
You cannot. 

Unfortunately, to have the radio capable of receiving signals, it has to be powered up. The datasheet states a typical consumption of 17.5 mA for the radio in receive mode, even with the CPU sleeping.

You can do some tricks with turning the radio off for short periods of time, though. 

For example, if you run the radio until you see the other node you want to talk to, you could have the two nodes agree to queue transmissions between the nodes for a period of time, and then both reactivate their radio after a set period of time.

Basically, if both nodes agree to sleep for say 10 ms, and then activate their radios for 1 ms, you can reduce power consumption by 90%, at the cost of a equivalent loss of data bandwith. Since this is smart-home stuff, I'd assume it's much lower bandwith then the theoretical radio throughput, it will likely not be an issue.

You would want the nodes to resynchronize at every interval, to minimize clock drift.