Vesicular monoamine transporter 1 is responsible for storage of 5-hydroxytryptamine in rat pinealocytes.
Vesicular monoamine transporters (VMATs) are involved in chemical transduction in monoaminergic neurons and various endocrine cells through the storage of monoamines in secretory vesicles. Mammalian pinealocytes contain more 5-hydroxytryptamine (5-HT) than any other cells and are expected to contain VMAT, although no information is available so far. Upon the addition of ATP, radiolabeled 5-HT was taken up by a particulate fraction prepared from cultured rat pinealocytes. The 5-HT uptake was inhibited significantly by bafilomycin A1 (an inhibitor of vacuolar H+-ATPase), 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (a proton conductor), or reserpine (an inhibitor of VMAT). RT-PCR analysis suggested that VMAT type 1 (VMAT1), but not type 2, is expressed. Antibodies against VMAT1 recognized a single polypeptide with an apparent molecular mass of approximately 55 kDa, and specifically immunostained pinealocytes. VMAT1 immunoreactivity was high in the vesicular structures in the varicosities of long branching processes and was associated with 5-HT, but not with synaptophysin, a marker protein for microvesicles. The 5-HT immunoreactivity in the long branching processes disappeared upon incubation with reserpine. These results indicate that 5-HT, at least in part, is stored in vesicles other than microvesicles in pinealocytes through a mechanism similar to that of various secretory vesicles.
Hayashi
M
M
Department of Biochemistry, Faculty of Pharmaceutical Sciences, CREST, Japan Science and Technology Corporation, Okayama University.
Haga
M
M
Yatsushiro
S
S
Yamamoto
A
A
Moriyama
Y
Y
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D018698:Glutamic Acid / Q000378:metabolism; D018942:Macrolides; D008550:Melatonin / Q000096:biosynthesis*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D026901:Membrane Transport Proteins; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D009479:Neuropeptides; D009570:Nitriles / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology; D016716:PC12 Cells / Q000187:drug effects; D010870:Pineal Gland / Q000166:cytology / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012701:Serotonin / Q000378:metabolism*; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins
D000900:Anti-Bacterial Agents; D018942:Macrolides; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009479:Neuropeptides; D009570:Nitriles; C493451:Slc18a1 protein, rat; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins; D012701:Serotonin; D018698:Glutamic Acid; C001784:SF 6847; C040929:bafilomycin A1; D012110:Reserpine; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D008550:Melatonin; D009638:Norepinephrine