Receptor Biology Laboratory, Department of Physiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. hwang@mayo.edu|Receptor Biology Laboratory, Department of Physiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. hwang@mayo.edu|Receptor Biology Laboratory, Department of Physiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. hwang@mayo.edu|Receptor Biology Laboratory, Department of Physiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. hwang@mayo.edu|Receptor Biology Laboratory, Department of Physiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. hwang@mayo.edu