Glycogen synthase kinase 3beta interacts with and phosphorylates the spindle-associated protein astrin.
Emerging evidence shows that glycogen synthase kinase 3beta (GSK3beta) is involved in mitotic division and that inhibiting of GSK3beta kinase activity causes defects in spindle microtubule length and chromosome alignment. However, the purpose of GSK3beta involvement in spindle microtubule assembly and accurate chromosome segregation remains obscure. Here, we report that GSK3beta interacts with the spindle-associated protein Astrin both in vitro and in vivo. Additionally, Astrin acts as a substrate for GSK3beta and is phosphorylated at Thr-111, Thr-937 ((S/T)P motif) and Ser-974/Thr-978 ((S/T)XXX(S/T)-p motif; p is a phosphorylatable residue). Inhibition of GSK3beta impairs spindle and kinetochore accumulation of Astrin and spindle formation at mitosis, suggesting that Astrin association with the spindle microtubule and kinetochore may be dependent on phosphorylation by GSK3beta. Conversely, depletion of Astrin by small interfering RNA has no detectable influence on the localization of GSK3beta. Interestingly, in vitro assays demonstrated that Astrin enhances GSK3beta-mediated phosphorylation of other substrates. Moreover, we showed that coexpression of Astrin and GSK3beta differentially increases GSK3beta-mediated Tau phosphorylation on an unprimed site. Collectively, these data indicate that GSK3beta interacts with and phosphorylates the spindle-associated protein Astrin, resulting in targeting Astrin to the spindle microtubules and kinetochores. In turn, the GSK3beta-Astrin complex may also facilitate further physiological and pathological phosphorylation.
Graduate Institute of Biochemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
Tai-Shan
TS
Cheng
Yun-Ling
YL
Hsiao
Ching-Chih
CC
Lin
Chang-Tze Ricky
CT
Yu
Ching-Mei
CM
Hsu
Mau-Sun
MS
Chang
Chu-I
CI
Lee
Chi-Ying F
CY
Huang
Shen-Long
SL
Howng
Yi-Ren
YR
Hong
D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002877:Chromosomes, Human / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000502:physiology*; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D034741:RNA, Small Interfering; C486663:SPAG5 protein, human; D016875:tau Proteins; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3