Molecular determinant for run‐down of L‐type Ca2+ channels localized in the carboxyl terminus of the α1C subunit
KJF Kepplinger, G Förstner, H Kahr… - The Journal of …, 2000 - Wiley Online Library
KJF Kepplinger, G Förstner, H Kahr, K Leitner, P Pammer, K Groschner, NM Soldatov…
The Journal of Physiology, 2000•Wiley Online Library1 The role of the sequence 1572‐1651 in the C‐terminal tail of the α1C subunit in run‐down
of Ca2+ channels was studied by comparing functional properties of the conventional α1C,
77 channel with those of three isoforms carrying alterations in this motif. 2 The pore‐forming
α1C subunits were co‐expressed with α2δ and β2a subunits in HEK‐tsA201 cells, a
subclone of the human embryonic kidney cell line, and studied by whole‐cell and single‐
channel patch‐clamp techniques. 3 Replacement of amino acids 1572‐1651 in α1C, 77 with …
of Ca2+ channels was studied by comparing functional properties of the conventional α1C,
77 channel with those of three isoforms carrying alterations in this motif. 2 The pore‐forming
α1C subunits were co‐expressed with α2δ and β2a subunits in HEK‐tsA201 cells, a
subclone of the human embryonic kidney cell line, and studied by whole‐cell and single‐
channel patch‐clamp techniques. 3 Replacement of amino acids 1572‐1651 in α1C, 77 with …
- 1The role of the sequence 1572‐1651 in the C‐terminal tail of the α1C subunit in run‐down of Ca2+ channels was studied by comparing functional properties of the conventional α1C,77 channel with those of three isoforms carrying alterations in this motif.
- 2The pore‐forming α1C subunits were co‐expressed with α2δ and β2a subunits in HEK‐tsA201 cells, a subclone of the human embryonic kidney cell line, and studied by whole‐cell and single‐channel patch‐clamp techniques.
- 3Replacement of amino acids 1572‐1651 in α1C,77 with 81 different amino acids leading to α1C,86 significantly altered run‐down behaviour. Run‐down of Ba2+ currents was rapid with α1C,77 channels, but was slow with α1C,86.
- 4Transfer of the α1C,86 segments L (amino acids 1572‐1598) or K (amino acids 1595‐1652) into the α1C,77 channel yielded α1C,77L and α1C,77K channels, respectively, the run‐down of which resembled more that of α1C,77. These results demonstrate that a large stretch of sequence between residues 1572 and 1652 of α1C,86 renders Ca2+ channels markedly resistant to run‐down.
- 5The protease inhibitor calpastatin added together with ATP was able to reverse the run‐down of α1C,77 channels. Calpastatin expression was demonstrated in the HEK‐tsA cells by Western blot analysis.
- 6These results indicate a significant role of the C‐terminal sequence 1572‐1651 of the α1C subunit in run‐down of L‐type Ca2+ channels and suggest this sequence as a target site for a modulatory effect by endogenous calpastatin.
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