Association of Kv1.5 and Kv1.3 contributes to the major voltage-dependent K+ channel in macrophages.
Voltage-dependent K(+) (Kv) currents in macrophages are mainly mediated by Kv1.3, but biophysical properties indicate that the channel composition could be different from that of T-lymphocytes. K(+) currents in mouse bone marrow-derived and Raw-264.7 macrophages are sensitive to Kv1.3 blockers, but unlike T-cells, macrophages express Kv1.5. Because Shaker subunits (Kv1) may form heterotetrameric complexes, we investigated whether Kv1.5 has a function in Kv currents in macrophages. Kv1.3 and Kv1.5 co-localize at the membrane, and half-activation voltages and pharmacology indicate that K(+) currents may be accounted for by various Kv complexes in macrophages. Co-expression of Kv1.3 and Kv1.5 in human embryonic kidney 293 cells showed that the presence of Kv1.5 leads to a positive shift in K(+) current half-activation voltages and that, like Kv1.3, Kv1.3/Kv1.5 heteromers are sensitive to r-margatoxin. In addition, both proteins co-immunoprecipitate and co-localize. Fluorescence resonance energy transfer studies further demonstrated that Kv1.5 and Kv1.3 form heterotetramers. Electrophysiological and pharmacological studies of different ratios of Kv1.3 and Kv1.5 co-expressed in Xenopus oocytes suggest that various hybrids might be responsible for K(+) currents in macrophages. Tumor necrosis factor-alpha-induced activation of macrophages increased Kv1.3 with no changes in Kv.1.5, which is consistent with a hyperpolarized shift in half-activation voltage and a lower IC(50) for margatoxin. Taken together, our results demonstrate that Kv1.5 co-associates with Kv1.3, generating functional heterotetramers in macrophages. Changes in the oligomeric composition of functional Kv channels would give rise to different biophysical and pharmacological properties, which could determine specific cellular responses.
Vicente
Rubén
R
Molecular Physiology Laboratory, Departament de Bioquiámica i Biologia Molecular, Departament de Fisiologia, and Unitat de Reconeixement Molecular in situ, Serveis Cientificotècnics Universitat de Barcelona, E-08028 Barcelona, Spain.
Escalada
Artur
A
Villalonga
Nuria
N
Texidó
Laura
L
Roura-Ferrer
Meritxell
M
Martín-Satué
Mireia
M
López-Iglesias
Carmen
C
Soler
Concepció
C
Solsona
Carles
C
Tamkun
Michael M
MM
Felipe
Antonio
A
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D051664:Kv1.3 Potassium Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051666:Kv1.5 Potassium Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000648:ultrastructure; D008564:Membrane Potentials; D051379:Mice; D008807:Mice, Inbred BALB C; D016253:Microscopy, Immunoelectron; D009865:Oocytes / Q000378:metabolism; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014982:Xenopus laevis
D017931:DNA Primers; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D021122:Protein Subunits; D011994:Recombinant Proteins