Involvement of Cyclic Adenosine Monophosphate-Dependent Protein Kinase A and Pertussis Toxin-Sensitive G Proteins in the Migratory Response of Human CD14+ Mononuclear Cells to Katacalcin

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Abstract
Katacalcin (KC) belongs to a small family of polypeptides that are encoded by the calc-1 gene and also include calcitonin (CT) and procalcitonin NH2-terminal cleavage peptide (N-ProCT). Biological roles of KC or N-ProCT are unknown. To determine whether these polypeptides affect leukocyte function, forearm venous blood polymorphonuclear neutrophils and CD14+ peripheral blood mononuclear cells (PBMCs) were isolated from healthy human donors. Cell migration was assessed in a blindwell chemotaxis chamber using nitrocellulose micropore filters. Cellular levels of cyclic adenosine monophosphate (cAMP) were measured by HPLC; activation of protein kinase A was studied by Western blot. Fluorochrome-labeled peptide binding to cells was studied by fluorescence-activated cell sorting (FACS) and intracellular calcium transients were studied by confocal microscopy with FLUO-3. KC elicited concentration-dependent migration of CD14+ PBMC at concentrations from the atomolar to the micromolar range and deactivated attractant-induced chemotaxis. CT N-terminal flanking peptide had no such effect. Neutrophils did not migrate toward any of those peptides and their oxygen-free radical release was not affected as measured fluorometrically. Functional responses of CD14+ PBMC to KC correlated to forskolin-sensitive cAMP accumulation in cells and were inhibited by protein kinase A inhibitor (PKI) and Rp diastereomer of adenosine 3',5'-cyclic monophosphorothioate. Treatment of CD14+ PBMC with KC activated protein kinase A(C alpha). Intracellular calcium was decreased with CT, KC, and procalcitonin (PCT). Binding studies showed that KC might share the binding site with CT and PCT. Data indicate that KC regulates human CD14+ PBMC migration via signaling events involving protein kinase A-dependent cAMP pathways.