Continual signaling is responsible for constitutive ERK phosphorylation in B-1a cells

Mol Immunol. 2009 Sep;46(15):3029-36. doi: 10.1016/j.molimm.2009.06.011. Epub 2009 Jul 9.


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

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • B-Lymphocytes / drug effects
  • B-Lymphocytes / metabolism*
  • B7-2 Antigen / drug effects
  • B7-2 Antigen / metabolism
  • CD5 Antigens / metabolism
  • Enzyme Inhibitors / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Phospholipase C gamma / antagonists & inhibitors
  • Phospholipase C gamma / metabolism
  • Phosphoric Monoester Hydrolases / antagonists & inhibitors
  • Phosphoric Monoester Hydrolases / metabolism
  • Phosphorylation / drug effects
  • Phosphorylation / physiology*
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Syk Kinase
  • Vanadates / pharmacology
  • src-Family Kinases / antagonists & inhibitors
  • src-Family Kinases / metabolism


  • B7-2 Antigen
  • CD5 Antigens
  • Cd5 protein, mouse
  • Cd86 protein, mouse
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • pervanadate
  • Vanadates
  • Protein-Tyrosine Kinases
  • Syk Kinase
  • Syk protein, mouse
  • src-Family Kinases
  • Extracellular Signal-Regulated MAP Kinases
  • Phosphoric Monoester Hydrolases
  • Phospholipase C gamma