Gi protein alpha subunit is a family of heterotrimeric G protein alpha subunits. Gi proteins primarily inhibit the cAMP dependent pathway by inhibiting adenylyl cyclase activity, resulting in decreased activity of cAMP-dependent protein kinase (PKA). This family is also commonly called the Gi/o family or Gi/o/z/t family to include closely related family members. G alpha subunits may be referred to as Gi alpha, Gαi, or Giα.