Abstract
Background: A large number of phospholipase C (PLC) enzymes, both mRNA transcripts and proteins, have been detected in osteoblasts, corroborating the importance of calcium regulation in bone tissue. MG-63 and SaOS-2 human osteosarcoma cell lines are actually considered osteoblast-like cells, and are therefore widely used as experimental models for osteoblasts. Objectives: Our aim was to verify whether MG-63 or SaOS-2 cells might also represent appropriate experimental osteoblast models for signal transduction studies, with special regard to the phosphoinositide (PI) pathway. We analyzed the expression and the subcellular distribution of enzymes related to calcium signal transduction (the PI-specific PLC family), which are known to possess high cell/tissue specificity. Materials and Methods: The expression of PLC genes was analyzed by performing RT-PCR experiments. The presence of PLC enzymes and their subcellular distribution within the cells was analyzed with immunofluorescence experiments. Conclusions: MG-63 and SaOS-2 osteosarcoma cell lines might not represent appropriate experimental models for studies that aim to analyze signal transduction in osteoblasts.
Highlights
A large number of phospholipase C (PLC) enzymes, both mRNA transcripts and proteins, have been detected in osteoblasts, corroborating the importance of calcium regulation in bone tissue
The following proteins were detected in the cytoplasm: PLC β1, PLC β4, PLC γ1, PLC δ1, and PLC η1
PLC β3 was detected at the perinuclear level, while PLC η2 was detected at the membrane level (Figure 2)
Summary
A large number of phospholipase C (PLC) enzymes, both mRNA transcripts and proteins, have been detected in osteoblasts, corroborating the importance of calcium regulation in bone tissue. We analyzed the expression and the subcellular distribution of enzymes related to calcium signal transduction (the PI-specific PLC family), which are known to possess high cell/tissue specificity. Osteoblasts play the pivotal role of secreting the matrix components in osseous tissues In addition to their involvement in bone formation and mineralization, osteoblasts can further differentiate into osteocytes and can provide crucial factors for osteoclast differentiation [1,2,3]. The complex network of signal transduction pathways that regulate calcium concentration has recently attracted great attention, including the phosphoinositide (PI) pathway and the related PI-specific phospholipase C (PLC) enzyme family. DAG can be further cleaved to release arachidonic acid [10] or can activate serine/threonine calcium-dependent protein kinase C enzymes (PKC), influenced by the IP3-induced calcium increase
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