The vesicular monoamine content regulates VMAT2 activity through Galphaq in mouse platelets. Evidence for autoregulation of vesicular transmitter uptake

J Biol Chem. 2003 May 2;278(18):15850-8. doi: 10.1074/jbc.M212816200. Epub 2003 Feb 25.

Abstract

Variations in the neurotransmitter content of secretory vesicles enable neurons to adapt to network changes. Vesicular content may be modulated by vesicle-associated Go(2), which down-regulates the activity of the vesicular monoamine transmitter transporters VMAT1 in neuroendocrine cells and VMAT2 in neurons. Blood platelets resemble serotonergic neurons with respect to transmitter storage and release. In streptolysin O-permeabilized platelets, VMAT2 activity is also down-regulated by the G protein activator guanosine 5'-(beta(i)gamma-imido)triphosphate (GMppNp). Using serotonin-depleted platelets from peripheral tryptophan hydroxylase knockout (Tph1-/-) mice, we show here that the vesicular filling initiates the G protein-mediated down-regulation of VMAT2 activity. GMppNp did not influence VMAT2 activity in naive platelets from Tph1-/- mice. GMppNp-mediated inhibition could be reconstituted, however, when preloading Tph1-/- platelets with serotonin or noradrenaline. Galpha(q) mediates the down-regulation of VMAT2 activity as revealed from uptake studies performed with platelets from Galpha(q) deletion mutants. Serotonergic, noradrenergic, as well as thromboxane A(2) receptors are not directly involved in the down-regulation of VMAT2 activity. It is concluded that in platelets the vesicle itself regulates transmitter transporter activity via its content and vesicle-associated Galpha(q).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Platelets / metabolism*
  • Female
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • Guanylyl Imidodiphosphate / pharmacology
  • Heterotrimeric GTP-Binding Proteins / physiology*
  • Homeostasis
  • Male
  • Membrane Glycoproteins / metabolism*
  • Membrane Transport Proteins*
  • Mice
  • Neuropeptides*
  • Receptor, Serotonin, 5-HT2A
  • Receptors, Serotonin / physiology
  • Secretory Vesicles / chemistry
  • Secretory Vesicles / physiology*
  • Serotonin / analysis
  • Serotonin / metabolism*
  • Tryptophan Hydroxylase / physiology
  • Vesicular Biogenic Amine Transport Proteins
  • Vesicular Monoamine Transport Proteins

Substances

  • Membrane Glycoproteins
  • Membrane Transport Proteins
  • Neuropeptides
  • Receptor, Serotonin, 5-HT2A
  • Receptors, Serotonin
  • Slc18a1 protein, mouse
  • Slc18a2 protein, mouse
  • Vesicular Biogenic Amine Transport Proteins
  • Vesicular Monoamine Transport Proteins
  • Serotonin
  • Guanylyl Imidodiphosphate
  • Tryptophan Hydroxylase
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • Heterotrimeric GTP-Binding Proteins