Abstract
B-1a cells constitutively express phosphorylated, activated ERK, but the origin of pERK in B-1 cells has not been determined. To address this issue, we examined specific mediators of intracellular signaling in unmanipulated B-1a cells. We found that constitutive pERK was rapidly lost from B-1a cells following addition of metabolic inhibitors that block src kinase, Syk, PI-3K, and PLC function. We examined Syk and PLC in more detail and found rapid accumulation of phosphorylated forms of these molecules in B-1a cells, but not B-2 cells, when phosphatase activity was inhibited, and this change occurred in the majority of B-1a cells. Further, we showed that inhibition of src kinase activity eliminated "downstream" pSyk and pPLC accumulation in phosphatase-inhibited B-1a cells, indicating a pathway connection. CD86 expression is greater on B-1 than B-2 cells and plays a role in antigen presentation by B-1 cells to T cells. We found that when Syk or PI-3K was inhibited, CD86 expression was diminished in a reversible fashion. All together, these results indicate that continual activation of intracellular signaling leads to constitutive activation of ERK in B-1 cells, with attendant consequences for co-stimulatory molecule expression.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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B-Lymphocytes / drug effects
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B-Lymphocytes / metabolism*
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B7-2 Antigen / drug effects
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B7-2 Antigen / metabolism
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CD5 Antigens / metabolism
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Enzyme Inhibitors / pharmacology
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Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
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Extracellular Signal-Regulated MAP Kinases / metabolism*
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Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
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Intracellular Signaling Peptides and Proteins / metabolism
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Male
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Mice
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Mice, Inbred BALB C
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphoinositide-3 Kinase Inhibitors
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Phospholipase C gamma / antagonists & inhibitors
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Phospholipase C gamma / metabolism
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Phosphoric Monoester Hydrolases / antagonists & inhibitors
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Phosphoric Monoester Hydrolases / metabolism
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Phosphorylation / drug effects
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Phosphorylation / physiology*
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology*
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Syk Kinase
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Vanadates / pharmacology
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src-Family Kinases / antagonists & inhibitors
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src-Family Kinases / metabolism
Substances
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B7-2 Antigen
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CD5 Antigens
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Cd5 protein, mouse
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Cd86 protein, mouse
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Enzyme Inhibitors
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Intracellular Signaling Peptides and Proteins
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Phosphoinositide-3 Kinase Inhibitors
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pervanadate
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Vanadates
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Protein-Tyrosine Kinases
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Syk Kinase
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Syk protein, mouse
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src-Family Kinases
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Extracellular Signal-Regulated MAP Kinases
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Phosphoric Monoester Hydrolases
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Phospholipase C gamma