J. Biol. Chem., Vol. 265, Issue 16, 9165-9169, 06, 1990
Presence of 5-hydroxytryptamine (serotonin) transport coupled with vacuolar-type H(+)-ATPase in neurosecretory granules from bovine posterior pituitary
Y Moriyama and M Futai
Department of Organic Chemistry and Biochemistry, Osaka University, Japan.
Electrogenic H(+)-ATPase was found in neurosecretory granules from bovine
posterior pituitary. This enzyme was sensitive to bafilomycin, a specific
inhibitor of vacuolar H(+)-ATPase, and was inactivated completely by cold
treatment in the presence of MgATP and NaNO3. Immunoblot analysis showed
the presence of immunologically identical polypeptides (72, 57, and 34 kDa)
in the ATPases of the neurosecretory granules and chromaffin granules. The
granules showed MgATP-dependent activity for 5-hydroxytryptamine
(serotonin) uptake. This uptake was temperature-dependent and showed
saturation kinetics (apparent Km for 5- hydroxytryptamine, 2 microM) and
counter-flow. Reserpine and tetrabenazine at 1 microM inhibited the uptake,
whereas imipramine at 2 microM had no effect. Dopamine, epinephrine and
norepinephrine were also inhibitory. The uptake was abolished by various
treatments that dissipated the electrochemical H+ gradient or inhibited the
H(+)- ATPase. These results indicate that a vacuolar type H(+)-ATPase in
the neurosecretory granules forms an electrochemical H+ gradient that
drives 5-hydroxytryptamine uptake by a specific transport system. A similar
granular fraction from the anterior pituitary had no ATP- dependent
activity for 5-hydroxytryptamine uptake.