Pyk2 and Megakaryocytes Regulate Osteoblast Differentiation and Migration Via Distinct and Overlapping Mechanisms

Pierre P. Eleniste, Vruti Patel, Sumana Posritong, Odette Zero, Heather Largura, Ying Hua Cheng, Evan R. Himes, Matthew Hamilton, Jenna Baughman, Melissa A. Kacena, Angela Bruzzaniti

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Osteoblast differentiation and migration are necessary for bone formation during bone remodeling. Mice lacking the proline-rich tyrosine kinase Pyk2 (Pyk2-KO) have increased bone mass, in part due to increased osteoblast proliferation. Megakaryocytes (MKs), the platelet-producing cells, also promote osteoblast proliferation in vitro and bone-formation in vivo via a pathway that involves Pyk2. In the current study, we examined the mechanism of action of Pyk2, and the role of MKs, on osteoblast differentiation and migration. We found that Pyk2-KO osteoblasts express elevated alkaline phosphatase (ALP), type I collagen and osteocalcin mRNA levels as well as increased ALP activity, and mineralization, confirming that Pyk2 negatively regulates osteoblast function. Since Pyk2 Y402 phosphorylation is important for its catalytic activity and for its protein-scaffolding functions, we expressed the phosphorylation-mutant (Pyk2Y402F) and kinase-mutant (Pyk2K457A) in Pyk2-KO osteoblasts. Both Pyk2Y402F and Pyk2K457A reduced ALP activity, whereas only kinase-inactive Pyk2K457A inhibited Pyk2-KO osteoblast migration. Consistent with a role for Pyk2 on ALP activity, co-culture of MKs with osteoblasts led to a decrease in the level of phosphorylated Pyk2 (pY402) as well as a decrease in ALP activity. Although, Pyk2-KO osteoblasts exhibited increased migration compared to wild-type osteoblasts, Pyk2 expression was not required necessary for the ability of MKs to stimulate osteoblast migration. Together, these data suggest that osteoblast differentiation and migration are inversely regulated by MKs via distinct Pyk2-dependent and independent signaling pathways. Novel drugs that distinguish between the kinase-dependent or protein-scaffolding functions of Pyk2 may provide therapeutic specificity for the control of bone-related diseases.

Original languageEnglish (US)
Pages (from-to)1396-1406
Number of pages11
JournalJournal of Cellular Biochemistry
Volume117
Issue number6
DOIs
StatePublished - Jun 1 2016

Keywords

  • ALKALINE PHOSPHATASE
  • BONE FORMATION
  • MINERALIZATION
  • PHOSPHORYLATION
  • TYROSINE KINASE

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Eleniste, P. P., Patel, V., Posritong, S., Zero, O., Largura, H., Cheng, Y. H., Himes, E. R., Hamilton, M., Baughman, J., Kacena, M. A., & Bruzzaniti, A. (2016). Pyk2 and Megakaryocytes Regulate Osteoblast Differentiation and Migration Via Distinct and Overlapping Mechanisms. Journal of Cellular Biochemistry, 117(6), 1396-1406. https://doi.org/10.1002/jcb.25430