Ca(2+) signaling in antigen receptor-activated B lymphocytes.
B cells respond to antigen stimulation with mobilization of the Ca(2+) second messenger in two phases operated by two distinct sets of effector proteins. First, an antigen receptor-specific Ca(2+) initiation complex is assembled, activated, and targeted to the plasma membrane to trigger the transient release of Ca(2+) from intracellular stores of the endoplasmic reticulum. Second, more ubiquitously expressed Ca(2+) channels of the plasma membrane are opened to allow for sustained Ca(2+) influx from the extracellular medium. Depending on the developmental stage of the B cell, the kinetics and profile of the two phases are adjusted at multiple levels of positive and negative regulation. A molecular basis for the Ca(2+) signaling plasticity is provided by cytosolic and transmembrane adapter proteins. They act as signal organizers, which control enzyme/substrate interactions by directing the different signaling modules into specific subcellular compartments. These arrangements orchestrate a graduated activation of Ca(2+)-sensitive downstream pathways, which ultimately determine appropriate cellular responses, namely elimination of autoreactive B cells or proliferation and differentiation of immunocompetent B cells into antibody-secreting plasma cells.
Engelke
Michael
M
Georg August University of Göttingen, Institute of Cellular and Molecular Immunology, Göttingen, Germany.
Engels
Niklas
N
Dittmann
Kai
K
Stork
Björn
B
Wienands
Jürgen
J
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D020013:Calcium Signaling / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D051966:Phospholipase C gamma / Q000378:metabolism; D011485:Protein Binding; D011947:Receptors, Antigen, B-Cell / Q000276:immunology* / Q000378:metabolism*
D011947:Receptors, Antigen, B-Cell; D051966:Phospholipase C gamma