Identification and characterization of CKLiK, a novel granulocyte Ca++/calmodulin-dependent kinase

Human granulocytes are characterized by a variety of specific effector func tions involved in host defense, Several widely expressed protein kinases ha ve been implicated in the regulation of these effector functions. A polymer ase chain reaction-based strategy was used to identify novel granulocyte-sp ecific kinases, A novel protein kinase complementary DNA with an open readi ng frame of 357 amino acids was identified with homology to calcium-calmodu lin-dependent kinase I(CaMKI), This has been termed CaMKI-like kinase (CKLi K). Analysis of CKLiK messenger RNA (mRNA) expression in hematopoietic cell s demonstrated an almost exclusive expression in human polymorphonuclear le ukocytes (PMN). Up-regulation of CKLiK mRNA occurs during neutrophilic diff erentiation of CD34(+) stem cells. CKLiK kinase activity was dependent on C a++ and calmodulin as analyzed by in vitro phosphorylation of cyclic adenos ine monophosphate responsive element modulator (CREM), Furthermore, CKLiK-t ransfected cells treated with ionomycin demonstrated an induction of CRE-bi nding protein (CREB) transcriptional activity compared to control cells. Ad ditionally, CaMK-kinase alpha enhanced CKLiK activity. In vivo activation o f CKLiK was shown by addition of interleukin (li)-8 to a myeloid cell line stably expressing CKLiK. Furthermore inducible activation of CKLiK was suff icient to induce extracellular signal-related kinase (ERK) mitogen-activate d protein (MAP) kinase activity. These data identify a novel Ca++/calmoduli n-dependent PMN-specific kinase that may play a role in Ca++-mediated regul ation of human granulocyte functions. (C) 2000 by The American Society of H ematology.