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Amyloid beta protein (25-35) phosphorylates MARCKS through tyrosine kinase-activated protein kinase C signaling
Abstract:
Myristoylated alanine-rich C kinase substrate (MARCKS) is a widely distributed specific protein kinase C (PKC) substrate and has been implicated in membrane trafficking, cell motility, secretion, cell cycle, and transformation. We found that amyloid beta protein (A beta) (25-35) and A beta (1-40) phosphorylate MARCKS in primary cultured rat microglia. Treatment of microglia with A beta (25-35) at 10 nM or 12-O-tetradecanoylphorbol 13-acetate (1.6 nM) led to phosphorylation of MARCKS, an event inhibited by PKC inhibitors, staurosporine, calphostin C, and chelerythrine. The A beta (25-35)-induced phosphorylation of MARCKS was inhibited by pretreatment with the tyrosine kinase inhibitors genistein and herbimycin A, but not with pertussis toxin. PKC isoforms alpha, delta, and epsilon were identified in microglia by immunocytochemistry and western blots using isoform-specific antibodies. PKC-delta was tyrosine-phosphorylated by the treatment of microglia for 10 min with A beta (25-35) at 10 nM. Other PKC isoforms alpha and epsilon were tyrosine-phosphorylated by A beta (25-35), but only to a small extent. We propose that a tyrosine kinase-activated PKC pathway is involved in the A beta (25-35)-induced phosphorylation of MARCKS in rat microglia.
Insights
Amyloid beta protein (Aβ) triggers the phosphorylation of Myristoylated alanine-rich C kinase substrate (MARCKS) in rat microglia. This process involves a tyrosine kinase-activated Protein Kinase C (PKC) pathway, impacting cellular functions.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Myristoylated alanine-rich C kinase substrate (MARCKS) is a key Protein Kinase C (PKC) substrate involved in critical cellular processes.
- Amyloid beta (Aβ) is implicated in neurological disorders and its effects on microglial signaling are under investigation.
Purpose of the Study:
- To investigate the effect of amyloid beta (Aβ) peptides on MARCKS phosphorylation in primary cultured rat microglia.
- To elucidate the specific signaling pathways, including PKC and tyrosine kinases, involved in Aβ-induced MARCKS phosphorylation.
Main Methods:
- Primary rat microglia cultures were treated with Aβ (25-35) or phorbol ester.
- MARCKS phosphorylation was assessed, and the effects of various inhibitors (PKC inhibitors, tyrosine kinase inhibitors) were evaluated.
- PKC isoform expression and tyrosine phosphorylation were analyzed using immunocytochemistry and Western blots.
Main Results:
- Aβ (25-35) and Aβ (1-40) induced MARCKS phosphorylation in microglia, an effect inhibited by PKC inhibitors.
- Tyrosine kinase inhibitors blocked Aβ (25-35)-induced MARCKS phosphorylation.
- PKC-delta was significantly tyrosine-phosphorylated by Aβ (25-35), with minor effects on PKC-alpha and epsilon.
Conclusions:
- Aβ peptides induce MARCKS phosphorylation in microglia via a pathway involving tyrosine kinases and PKC.
- The findings suggest a novel signaling mechanism in microglia activated by Aβ, potentially relevant to neuroinflammation and disease.