GK and type 1 diabetes mellitus: alters GK activity by ubiquitination, SUMOylation and citrullinationdiminishes insulin secretion by citrullinationincreased citrullinated GK in islets before the onset of hyperglycemiaautoantibodies against GK and citrullinated GK in NOD and T1D serumautoreactive T cells against citrullinated GK peptide in T1D patients