TY - JOUR
T1 - Polyamine uptake in cultured astrocytes: Characterization and modulation by protein kinases
AU - Dot, J.
AU - Lluch, M.
AU - Blanco, I.
AU - Rodriguez-Alvarez, J.
PY - 2000/1/1
Y1 - 2000/1/1
N2 - The properties and regulation of the polyamine transport system in brain are still poorly understood. The present study shows, for the first time, the existence of a polyamine transport system in cerebellar astrocytes and suggests that polyamine uptake is mediated by a single and saturable high-affinity transport system for putrescine, spermine, and spermidine (K(m) = 3.2, 1.2, and 1.8 μM, respectively). Although substitution of NaCl by choline chloride produced a decrease in the putrescine, spermine, and spermidine uptake, it seems that polyamine transport in cerebellar astrocytes is not mediated by an Na+ cotransport as in the presence of Na+ and cholinium, polyamine uptake was much lower than when measured in a sucrose-based medium. On the other hand, ouabain, gramicidin (a Na+ ionophore), and ionomycin (a Ca2+ ionophore) produced a strong inhibition of polyamine uptake, suggesting that membrane potential could have an important role in the functioning of the astroglial polyamine uptake system. Moreover, protein kinase C inhibition produced an enhancement of polyamine uptake, whereas stimulation of protein kinase C with phorbol esters inhibited polyamine uptake. Alternatively, the tyrosine kinase inhibitor genistein caused a marked reduction in the uptake. No effects on polyamine uptake were observed with inhibitors and activators of cyclic AMP-dependent protein kinase or when Ca2+/calmodulin-dependent protein kinase II was inhibited with KN-62. These results suggest that the polyamine uptake system in cerebellar astrocytes could be modulated by protein kinase C and tyrosine kinase activities.
AB - The properties and regulation of the polyamine transport system in brain are still poorly understood. The present study shows, for the first time, the existence of a polyamine transport system in cerebellar astrocytes and suggests that polyamine uptake is mediated by a single and saturable high-affinity transport system for putrescine, spermine, and spermidine (K(m) = 3.2, 1.2, and 1.8 μM, respectively). Although substitution of NaCl by choline chloride produced a decrease in the putrescine, spermine, and spermidine uptake, it seems that polyamine transport in cerebellar astrocytes is not mediated by an Na+ cotransport as in the presence of Na+ and cholinium, polyamine uptake was much lower than when measured in a sucrose-based medium. On the other hand, ouabain, gramicidin (a Na+ ionophore), and ionomycin (a Ca2+ ionophore) produced a strong inhibition of polyamine uptake, suggesting that membrane potential could have an important role in the functioning of the astroglial polyamine uptake system. Moreover, protein kinase C inhibition produced an enhancement of polyamine uptake, whereas stimulation of protein kinase C with phorbol esters inhibited polyamine uptake. Alternatively, the tyrosine kinase inhibitor genistein caused a marked reduction in the uptake. No effects on polyamine uptake were observed with inhibitors and activators of cyclic AMP-dependent protein kinase or when Ca2+/calmodulin-dependent protein kinase II was inhibited with KN-62. These results suggest that the polyamine uptake system in cerebellar astrocytes could be modulated by protein kinase C and tyrosine kinase activities.
KW - Astrocytes
KW - Polyamines
KW - Protein kinases
KW - Putrescine
KW - Spermidine
KW - Spermine
KW - Uptake
U2 - https://doi.org/10.1046/j.1471-4159.2000.0751917.x
DO - https://doi.org/10.1046/j.1471-4159.2000.0751917.x
M3 - Article
SN - 0022-3042
VL - 75
SP - 1917
EP - 1926
JO - Journal of Neurochemistry
JF - Journal of Neurochemistry
ER -