Abstract
BackgroundSkeletal muscle satellite cell-derived myoblasts are mainly responsible for postnatal muscle growth and injury-induced regeneration. Many intracellular signaling pathways are essential for myogenic differentiation, while a number of kinases are involved in this modulation process. Type I phosphatidylinositol 4-phosphate 5-kinase (PIP5KI) was identified as one of the key kinases involved in myogenic differentiation, but the underlying molecular mechanism is still unclear.MethodsPIP5K1α was quantified by quantitative reverse transcriptase PCR and western blot assay. Expression levels of myogenin and myosin heavy chain, which showed significant downregulation in PIP5K1α siRNA-mediated knockdown cells in western blot analysis, were confirmed by immunostaining. Phosphatidylinositol 4,5-bisphosphate in PIP5K1α siRNA-mediated knockdown cells was also measured by the PI(4,5)P2 Mass ELISA Kit. C2C12 cells were overexpressed with different forms of AKT, followed by western blot analysis on myogenin and myosin heavy chain, which reveals their function in myogenic differentiation. FLIPR assays are used to test the release of calcium in PIP5K1α siRNA-mediated knockdown cells after histamine or bradykinin treatment. Statistical significances between groups were determined by two-tailed Student’s t test.ResultsSince PIP5K1α was the major form in skeletal muscle, knockdown of PIP5K1α consistently inhibited myogenic differentiation while overexpression of PIP5K1α promoted differentiation and rescued the inhibitory effect of the siRNA. PIP5K1α was found to be required for AKT activation and calcium release, both of which were important for skeletal muscle differentiation.ConclusionsTaken together, these results suggest that PIP5K1α is an important regulator in myoblast differentiation.
Highlights
Skeletal muscle satellite cell-derived myoblasts are mainly responsible for postnatal muscle growth and injury-induced regeneration
Phosphatidylinositol 4 (PIP2) can be phosphorylated by phosphatidylinositol 3-kinase (PI3K) to generate PIP3, which is another lipid second messenger involved in cell growth, survival, and apoptosis [15]
PIP5K1α was upregulated during myoblast differentiation To explore the potential role of PIP5K1 isoforms in myogenic differentiation, we first examined their expression patterns
Summary
Skeletal muscle satellite cell-derived myoblasts are mainly responsible for postnatal muscle growth and injury-induced regeneration. Many intracellular signaling pathways are essential for myogenic differentiation, while a number of kinases are involved in this modulation process. Type I phosphatidylinositol 4-phosphate 5-kinase (PIP5KI) was identified as one of the key kinases involved in myogenic differentiation, but the underlying molecular mechanism is still unclear. Adult mammalian skeletal muscle could induce a rapid and extensive regeneration in response to severe damage. This muscle repair process occurs through the activation of muscle satellite cells quiescent in the basal lamina and the muscle fiber membrane of normal muscles. PIP2 can be phosphorylated by PI3K to generate PIP3, which is another lipid second messenger involved in cell growth, survival, and apoptosis [15]. PIP5K1 essentially regulates these processes by modulating the production of the multifunctional lipid messenger PIP2
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