Direct control of exocytosis by receptor-mediated activation of the heterotrimeric GTPases Gi and G(o) or by the expression of their active G alpha subunits.

AUTOR(ES)

Lang, J

RESUMO

The exocytotic release of potent hormones is a tightly controlled process. Its direct regulation without the involvement of second messengers would ensure rapid signal processing. In streptolysin O-permeabilized insulin-secreting cells, a preparation allowing dialysis of cytosolic macromolecules, activation of alpha 2-adrenergic receptors caused pertussis toxin-sensitive inhibition of calcium-induced exocytosis. This inhibition was mimicked very efficiently by the use of specific receptor-mimetic peptides, indicating the involvement of Gi and, to a lesser extent, of G(o). The regulation was exerted beyond the ATP-dependent step of exocytosis. In addition, low nanomolar amounts of pre-activated Gi/G(o) directly inhibited exocytosis. As transient overexpression of constitutively active mutants of G alpha i1, G alpha i2, G alpha i3 and G alpha o2 but not of G alpha o1 reproduced this regulation, the G alpha subunit alone is sufficient to induce inhibition. These results define exocytosis as an effector for heterotrimeric G-proteins and delineate the properties of the transduction pathway.

Documentos Relacionados

• Corrigendum: Direct control of exocytosis by receptor-mediated activation of the heterotrimeric GTPases Gi and Go or by the expression of their active Ga subunits
• Direct activation of trpl cation channels by G alpha11 subunits.
• Receptor-mediated regional sympathetic nerve activation by leptin.
• Receptor-mediated endocytosis.
• The Relative Role of Lymphocyte Granule Exocytosis versus Death Receptor-Mediated Cytotoxicity in Viral Pathophysiology