TRIB Pseudokinases Regulation and Function in Bovine Granulosa Cells

TRIB members (TRIB1, TRIB2 and TRIB3) represent atypical members of the serine/threonine kinase superfamily and are involved in multiple biological processes such as cell proliferation and differentiation. TRIB roles in GC are not fully investigated. We hypothesized that TRIB members play crucial roles in regulating GC activity and may activate separate signaling pathways. TRIB1 and TRIB3 are induced in GC of ovulatory follicles (OF) following hCG injection as compared to dominant follicles (DF) whereas TRIB2 is suppressed by hCG in OF. Protein analyses of cultured primary GC showed that luteinizing hormone (LH) treatment inhibited TRIB2 and induced TRIB3, while follicle-stimulating hormone (FSH) treatment increased TRIB2 and TRIB3 expression but at different times. These results demonstrate a different regulation of TRIB members during follicular development and in response to gonadotropins. TRIB3 inhibition via CRISPR/Cas9 showed a positive effect on AKT signaling pathway while showing negative effects on P38 MAPK signaling. Overall, TRIBs may play crucial roles in regulating GC function and activity and may activate separate signaling pathways, which impact follicular development, ovulation and luteinization.