The glycosylation of the extracellular loop of β2 subunits diversifies functional phenotypes of BK Channels.
Large-conductance Ca2+- and voltage-activated potassium (MaxiK or BK) channels are composed of a pore-forming α subunit (Slo) and 4 types of auxiliary β subunits or just a pore-forming α subunit. Although multiple N-linked glycosylation sites in the extracellular loop of β subunits have been identified, very little is known about how glycosylation influences the structure and function of BK channels. Using a combination of site-directed mutagenesis, western blot and patch-clamp recordings, we demonstrated that 3 sites in the extracellular loop of β2 subunit are N-glycosylated (N-X-T/S at N88, N96 and N119). Glycosylation of these sites strongly and differentially regulate gating kinetics, outward rectification, toxin sensitivity and physical association between the α and β2 subunits. We constructed a model and used molecular dynamics (MD) to simulate how the glycosylation facilitates the association of α/β2 subunits and modulates the dimension of the extracellular cavum above the pore of the channel, ultimately to modify biophysical and pharmacological properties of BK channels. Our results suggest that N-glycosylation of β2 subunits plays crucial roles in imparting functional heterogeneity of BK channels, and is potentially involved in the pathological phenotypes of carbohydrate metabolic diseases.
a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.|b Wuhan Foreign Languages School , Wuhan , Hubei , China.
Zhi-Gang
ZG
Huang
a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.
Hao-Wen
HW
Liu
a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.
Zhen-Zhen
ZZ
Yan
a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.
Sheng
S
Wang
c Program in Neurosciences and Mental Health, SickKids Research Institute and Department of Physiology , University of Toronto , Toronto , Ontario , Canada.
Lu-Yang
LY
Wang
a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.
Jiu-Ping
JP
Ding
D000595:Amino Acid Sequence; D000818:Animals; D018999:Charybdotoxin / Q000494:pharmacology; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000737:chemistry / Q000378:metabolism; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D056004:Molecular Dynamics Simulation; D010641:Phenotype; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D018999:Charybdotoxin
BK channels; association; glycosylation; mSlo1; β2
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