Mi-Kyoung Kim

A novel collagen-binding peptide promotes osteogenic differentiation via Ca2+/calmodulin-dependent protein kinase II/ERK/AP-1 signaling pathway in human bone marrow-derived mesenchymal stem cells.

The intracellular signaling events controlling human mesenchymal stem cell (hMSC) differentiation into osteoblasts are poorly understood. Collagen-binding domain is considered an essential component of bone mineralization. In the present study, we investigated the regulatory mechanism of osteoblastic differentiation of hMSC by the peptide with a novel collagen-binding motif derived from osteopontin. The peptide induced influx of extracellular Ca2+ via calcium channels and increased intracellular Ca2+ concentration ([Ca2+]i) independent of both pertussis toxin and phospholipase C, and activated ERK, which was inhibited by Ca2+/calmodulin-dependent protein kinase (CaMKII) antagonist, KN93. The peptide-induced increase of [Ca2+]i is correlated with ERK activation in a various cell types. The peptide stimulated the migration of hMSC but suppressed cell proliferation. Furthermore, the peptide increased the phosphorylation of cAMP-response element-binding protein, leading to a significant increase in the transactivation of cAMP-response element and serum response element. Ultimately, the peptide increased AP-1 transactivation, c-jun expression, and bone mineralization, which are suppressed by KN93. Taken together, these results indicate that the novel collagen-binding peptide promotes osteogenic differentiation via Ca2+/CaMKII/ERK/AP-1 signaling pathway in hMSC, suggesting the potential application in cell therapy for bone regeneration.

Lysophosphatidylethanolamine stimulates chemotactic migration and cellular invasion in SK-OV3 human ovarian cancer cells: involvement of pertussis toxin-sensitive G-protein coupled receptor.

We investigated whether lysophosphatidylethanolamine (LPE) modulates cellular signaling in different cell types. SK‐OV3 ovarian cancer cells and OVCAR‐3 ovarian cancer cells were responsive to LPE. LPE‐stimulated intracellular calcium concentration ([Ca2+]i) increase was inhibited by U‐73122, suggesting that LPE stimulates calcium signaling via phospholipase C activation. Moreover, pertussis toxin (PTX) almost completely inhibited [Ca2+]i increase by LPE, indicating the involvement of PTX‐sensitive G‐proteins. Furthermore, we found that LPE stimulated chemotactic migration and cellular invasion in SK‐OV3 ovarian cancer cells. We examined the role of lysophosphatidic acid receptors on LPE‐stimulated cellular responses using HepG2 cells transfected with different LPA receptors, and found that LPE failed to stimulate nuclear factor kappa B‐driven luciferase. We suggest that LPE stimulates a membrane bound receptor, different from well known LPA receptors, resulting in chemotactic migration and cellular invasion in SK‐OV3 ovarian cancer cells.

Expression and functional role of formyl peptide receptor in human bone marrow-derived mesenchymal stem cells.

We investigated the expression of formyl peptide receptor (FPR) and its functional role in human bone marrow‐derived mesenchymal stem cells (MSCs). We analyzed the expression of FPR by using ligand‐binding assay with radio‐labeled N‐formyl‐met‐leu‐phe (fMLF), and found that MSCs express FPR. FMLF stimulated intracellular calcium increase, mitogen‐activated protein kinases activation, and Akt activation, which were mediated by Gi proteins. MSCs were chemotactically migrated to fMLF. FMLF‐induced MSC chemotaxis was also completely inhibited by pertussis toxin, LY294002, and PD98059, indicating the role of Gi proteins, phosphoinositide 3‐kinase, and extracellular signal regulated protein kinase. N‐terminal fragment of annexin‐1, Anx‐1(2–26), an endogenous agonist for FPR, also induced chemotactic migration of MSCs. Thus MSCs express functional FPR, suggesting a new (patho)physiological role of FPR and its ligands in regulating MSC trafficking during induction of injured tissue repair.

Collagen-binding motif peptide, a cleavage product of osteopontin, stimulates human neutrophil chemotaxis via pertussis toxin-sensitive G protein-mediated signaling

The collagen‐binding motif (CBM) peptide, a cleavage product of osteopontin (OPN), stimulated intracellular calcium increase in human neutrophils. CBM peptide‐stimulated calcium was inhibited by pertussis toxin (PTX), suggesting the influence of PTX‐sensitive G‐proteins. In addition CBM peptide stimulated the chemotactic migration of human neutrophils and human monocytes. CBM peptide‐induced neutrophil chemotaxis was completely inhibited by PTX, once again indicating the influence of Gi proteins. CBM peptide was also found to induce mitogen activated protein kinase activation. CBM peptide‐induced neutrophil chemotaxis was mediated by p38 kinase as well as an extracellular signal‐regulated protein kinase. Taken together, the results suggest that a cleavage product of OPN, CBM peptide, initiates immune responses by inducing neutrophil trafficking via certain PTX‐sensitive cell surface receptors.