Phosphorylation mapping of laminin γ1-chain: Kinases, functional interaction sequences, and phosphorylation-interfering cancer mutations

We computationally predicted all phosphorylation sites in the sequence of the human laminin γ1-chain (LAMC1), and computationally identified, for the first time, all kinases for experimentally observed phosphorylated residues of the LAMC1 and all missense deleterious LAMC1 mutations found in different cancer types that interfere with LAMC1 phosphorylation. Also, we mapped the above data to all the biologically functional interaction sequences of the LAMC1. Five kinases (CKII, GPCRK1, PKA, PKC, and CKI) are most enriched for LAMC1 phosphorylation, and the significance of ecto-kinases in this process was emphasized. PKA and PKC targeted more residues inside and close to functional interaction sequences compared with other kinases and in the functional interaction sequence RPESFAIYKRTR. Most phosphorylation-interfering mutations were found in cutaneous melanoma and uterine endometrioid carcinoma. The mutation R255H interfered with the experimentally observed phosphorylation of LAMC1 inside the functional interaction sequence TDIRVTLNRLNTF, while the mutations S181Y and S213Y interfered with the experimentally observed phosphorylation of LAMC1 outside the functional interaction sequences. Mutations R359C,H, R589H, R657C,H, R663I,G, and T1207 interfered with the predicted phosphorylation inside or close to the functional interaction sequences, whereas other mutations interfered outside. PKA- and PKC-predicted phosphorylation was mostly interfered with by mutations inside functional interaction sequences. Phosphorylation-interfering mutations and functional interaction sequences were suggested to promote specific cancer types or cancer progression in general.