Title : Glycosylation of
GIRK1 at
Asn119 and
ROMK1 at
Asn117 has different consequences in
potassium channel function
Abstract :
- GIRK ( G protein-gated inward rectifier K(+) channel ) proteins play critical functional roles in heart and brain physiology
- Using antibodies directed to either GIRK1 or GIRK4 , site-directed mutagenesis, and specific glycosidases, we have investigated the effects of glycosylation in the biosynthesis and heteromerization of these proteins expressed in oocytes
- Both GIRK1 and GIRK4 have one extracellular consensus N-glycosylation site
- Using chimeras between GIRK1 and GIRK4 as well as a GIRK1 N-glycosylation mutant, we report that GIRK1 was glycosylated at Asn(119) , whereas GIRK4 was not glycosylated at Asn(132)
- GIRK1 membrane-spanning domain 1 was required for optimal glycosylation at Asn(119) because a chimera that contained GIRK4 membrane-spanning domain 1 significantly reduced the addition of a carbohydrate structure at this site
- This finding may partly account for the reason that GIRK4 is not glycosylated at Asn(132) , either as a homomer or when coexpressed with GIRK1
- When the GIRK1 ( N119Q ) mutant was coexpressed with GIRK4 , the biophysical properties of the heteromeric channel and the magnitude of the agonist-induced currents were similar to those of controls
- Thus, N-glycosylation of GIRK1 at Asn(119) does not appear to affect its physical association with GIRK4 , the routing of the heteromer to the cell surface, or heteromeric channel function, unlike the dramatic functional effects of N-glycosylation of ROMK1 at Asn(117) (Schwalbe, R. A., Wang, Z., Wible, B. A., and Brown, A. M. (1995) J. Biol
- Chem
- 270, 15336-15340)