ADRB2

In one line: The "adrenaline" receptor that opens airways and burns fat when switched on.

ADRB2 (the beta-2 adrenergic receptor) is one of the docks that adrenaline plugs into. Switch it on and airways open (which is why asthma inhalers target it), fat cells release their stored fuel, and the body burns a little hotter.

This is why fat-burners like clenbuterol and ephedrine work — they press this receptor to ramp up fat release and heat production. The same activation, though, speeds the heart and raises blood pressure, which is the downside of strong stimulant fat-burners.

Think of it as the "go faster, burn hotter" switch of your fight-or-flight system.