Complex sentence: PTP1B has been shown to act as a negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of the activated insulin receptor kinase.
Split into simpler sentences: PTP1B has been shown to act as a negative regulator of the insulin signaling pathway. PTP1B can dephosphorylate the phosphotyrosine residues of the activated insulin receptor kinase.