With the goal of throughput maximization in IEEE 802.11ac, this letter proposes a throughput-aware TXOP sharing scheme. This scheme performs joint link adaptation and scheduling of the downlink multiuser transmission such that MAC layer throughput is maximized, while the TXOP sharing rules of IEEE 802.11ac are satisfied. We show that this joint optimization problem is a non-convex mixed-integer nonlinear problem and solve it employing an ant colony optimization-based metaheuristic. The simulation results generated by IEEE 802.11ac channel and physical layer models substantiate a significant gain of this scheme in terms of MAC layer throughput.