Figure 1

The class I PI3K family. Class I PI3Ks are heterodimeric proteins and comprised of a catalytic p110 subunit complexed with a regulatory p85 or p101 subunit. The catalytic p110 subunit exists in four isoforms (α, β, δ, and γ), whereas the regulatory p85 subunit in three isoforms – p85, p55, and p50. Their corresponding upstream receptors and adaptor proteins are also indicated. RTK: receptor tyrosine kinase; GPCR: G-protein coupled receptors.