Proton-coupled polyamine antiporter involved in the translocation of polyamines from cytosol into secretory vesicles prior to their release via exocytosis. Uses the electrochemical proton gradient generated by a V-type proton-pumping ATPase to couple the efflux of protons with the uptake of a polyamine molecule . Facilitates vesicular storage of spermine and spermidine in astrocytes with an impact on glutamatergic neuronal transmission and memory formation  (By similarity). Upon antigen stimulation, regulates polyamine accumulation and release in mast cell secretory granules, which in turn potentiates mast cell degranulation and histamine secretion (By similarity).
Subcellular locations: Cytoplasmic vesicle, Secretory vesicle membrane, Cytoplasmic vesicle, Secretory vesicle, Synaptic vesicle membrane
Colocalizes with VAMP3 and VAMP8 in mast cell secretory granules, which are distinct from histamine- and serotonin-containing granules (By similarity). Partly colocalizes with SYP in synaptic vesicles in hippocampal neurons. Colocalizes with SYP and VAMP2 in secretory vesicles of astrocytes (By similarity).
Expressed in various tissues including lung, placenta, adrenal gland, liver, testis, and brain.