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FEBS Open Bio 2021 Apr 01;114:1093-1108. doi: 10.1002/2211-5463.13113.
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Identification of a unique endoplasmic retention motif in the Xenopus GIRK5 channel and its contribution to oocyte maturation.

Rangel-Garcia CI , Salvador C , Chavez-Garcia K , Diaz-Bello B , Lopez-Gonzalez Z , Vazquez-Cruz L , Angel Vazquez-Martinez J , Ortiz-Navarrete V , Riveros-Rosas H , Escobar LI .

G protein-activated inward-rectifying potassium (K+ ) channels (Kir3/GIRK) participate in cell excitability. The GIRK5 channel is present in Xenopus laevis oocytes. In an attempt to investigate the physiological role of GIRK5, we identified a noncanonical di-arginine endoplasmic reticulum (ER) retention motif (KRXY). This retention motif is located at the N-terminal region of GIRK5, coded by two small exons found only in X. laevis and X. tropicalis. These novel exons are expressed through use of an alternative transcription start site. Mutations in the sequence KRXY produced functional channels and induced progesterone-independent oocyte meiotic progression. The chimeric proteins enhanced green fluorescent protein (EGFP)-GIRK5-WT and the EGFP-GIRK5K13AR14A double mutant, were localized to the ER and the plasma membrane of the vegetal pole of the oocyte, respectively. Silencing of GIRK5 or blocking of this channel by external barium prevented progesterone-induced meiotic progression. The endogenous level of GIRK5 protein decreased through oocyte stages in prophase I augmenting by progesterone. In conclusion, we have identified a unique mechanism by which the expression pattern of a K+ channel evolved to control Xenopus oocyte maturation.

PubMed ID: 33565726
PMC ID: PMC8016131
Article link: FEBS Open Bio
Grant support: [+]

Species referenced: Xenopus tropicalis Xenopus laevis
Genes referenced: ccdc34 fli1 kcnj1 kcnj10 kcnj11 kcnj12 kcnj13 kcnj14 kcnj15 kcnj16 kcnj2 kcnj22 kcnj3 kcnj4 kcnj5 kcnj6 kcnj8 krt15.1 mapk1 rho tp53
GO keywords: inward rectifier potassium channel activity [+]
Antibodies: Mapk1 Ab13 Mapk1 Ab18

Article Images: [+] show captions
References [+] :
Assis, Nested genes and increasing organizational complexity of metazoan genomes. 2009, Pubmed