TY - JOUR
T1 - The cytoplasmic tail of large conductance, voltage- and Ca2+-activated K+ (MaxiK) channel is necessary for its cell surface expression
AU - Wang, Shao Xiong
AU - Ikeda, Masahiro
AU - Guggino, William B.
PY - 2003/1/24
Y1 - 2003/1/24
N2 - The large conductance, voltage- and Ca2+-activated K+ channel (MaxiK) is expressed in several renal segments and functions in cell volume regulation and flow-mediated K+ secretion. Previously, we cloned two MaxiK channel isoforms, named rbslo1 and rbslo2, from rabbit renal cells. rbslo1 has a 58-amino acid insertion after the S8 hydrophobic domain, whereas rbslo2 is truncated and cannot be activated. Here we use the sequence differences between the two variants to examine their plasma membrane processing. Plasma membrane localization of rbslo1 and 2 expressed in HEK293 cells was assayed by electrophysiology, immunocytochemistry, and biochemistry studies. Consistent with its functional silence, rbslo2 localized primarily within the cytoplasm, presumably in the endoplasmic reticulum and Golgi region. Coexpression with MaxiK β subunits did not alter the cellular localization of either rbslo1 or rbslo2. When rbslo1 and 2 are cotransfected in non-polarized cells, they colocalized primarily within the cell with only rbslo1 detected at the plasma membrane. When transfected into polarized, medullary-thick ascending limb (mTAIL) cells, rbslol is expressed at the apical membrane whereas the majority of rbslo2 localized throughout the cytoplasm. Given the high degree of similarity between the two isoforms, we conclude that the cytoplasmic tail of rbslol is important for the cell surface expression of MaxiK channels.
AB - The large conductance, voltage- and Ca2+-activated K+ channel (MaxiK) is expressed in several renal segments and functions in cell volume regulation and flow-mediated K+ secretion. Previously, we cloned two MaxiK channel isoforms, named rbslo1 and rbslo2, from rabbit renal cells. rbslo1 has a 58-amino acid insertion after the S8 hydrophobic domain, whereas rbslo2 is truncated and cannot be activated. Here we use the sequence differences between the two variants to examine their plasma membrane processing. Plasma membrane localization of rbslo1 and 2 expressed in HEK293 cells was assayed by electrophysiology, immunocytochemistry, and biochemistry studies. Consistent with its functional silence, rbslo2 localized primarily within the cytoplasm, presumably in the endoplasmic reticulum and Golgi region. Coexpression with MaxiK β subunits did not alter the cellular localization of either rbslo1 or rbslo2. When rbslo1 and 2 are cotransfected in non-polarized cells, they colocalized primarily within the cell with only rbslo1 detected at the plasma membrane. When transfected into polarized, medullary-thick ascending limb (mTAIL) cells, rbslol is expressed at the apical membrane whereas the majority of rbslo2 localized throughout the cytoplasm. Given the high degree of similarity between the two isoforms, we conclude that the cytoplasmic tail of rbslol is important for the cell surface expression of MaxiK channels.
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U2 - 10.1074/jbc.M208411200
DO - 10.1074/jbc.M208411200
M3 - Article
C2 - 12438308
AN - SCOPUS:0037462823
SN - 0021-9258
VL - 278
SP - 2713
EP - 2722
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 4
ER -