Heat Shock Protein 90 is Required for cAMP-Induced Differentiation in Rat Primary Schwann Cells

COUP‐TFII plays a role in cAMP‐induced Schwann cell differentiation and in vitro myelination by up‐regulating Krox20

“…The purity of cultured SC was determined by immunofluorescence staining with an anti‐S100β antibody. Immunofluorescence staining showed that more than 95% of cells expressed the specific SC marker S100β (Figure 1a), consistent with our previous study (Han et al, 2019). When SCs were treated with 1 mM db‐cAMP for indicated time periods, mRNA and protein levels of myelin‐related transcription factors (Oct6 and Krox20) and myelin proteins (MPZ and MAG) (Arroyo et al, 1998; Jagalur et al, 2011) were increased in a time‐dependent manner (Figure 1b,c).…”

“…Our observations suggest that COUP‐TFII is required for SC differentiation by db‐cAMP. Several reports have demonstrated that PKA, Hsp90, ErbB2, Gab1, and ERK are involved in the regulation of transcription factors, Oct6, and Krox20 in SC differentiation (Bacallao & Monje, 2013; Han et al, 2019; Howe & McCarthy, 2000; Ishii et al, 2021; Jagalur et al, 2011; Monk et al, 2015; Newbern et al, 2011; Newbern & Birchmeier, 2010; Shin et al, 2014). PKA, a downstream molecule of cAMP, plays an important role in the differentiation of SCs (Bacallao & Monje, 2013; Howe & McCarthy, 2000).…”

“…Especially, PKA can transactivate ErbB2‐Gab1 signaling without stimulating NRG1 type III during SC differentiation (Ghidinelli et al, 2017). Our previous study has demonstrated that db‐cAMP can induce SC differentiation through activation of PKA, up‐regulation of Hsp90, and activation of Gab1 (Han et al, 2019). Thus, we examined whether the expression of Hsp90, PKA catalytic subunit (PKA Cα) and p‐Gab1 after treatment of db‐cAMP (1 mM) in rat‐cultured SCs was regulated by COUP‐TFII.…”

“…Knockdown of Gab1 expression was performed using published procedures (Han et al, 2019). In brief, when primary SC reached 70% confluency, cells were transduced with lentiviral particles expressing Gab1‐shRNA (Gab1 MISSION shRNA Lentiviral Transduction Particles; Sigma‐Aldrich, TRCN0000100114, USA) or scrambled shRNA (MISSION® pLKO.1‐puro Empty Vector Control Transduction Particles; Sigma‐Aldrich, SHC001V, USA) for 18–24 h. The medium was replaced with a fresh DMEM containing 10% FBS and cultured for another 24 h. The medium was replaced with a growth medium (DMEM containing 1% FBS, 30 ng/ml NRG1, 5 μM forskolin) for 24 h and treated with db‐cAMP for 48 h. Cells were subsequently analyzed by Western blotting.…”

“…They can also induce SC differentiation via transactivation of ErbB2/ErbB3 signals independent of NRG1 type III in SCs, similar to the signaling pathway of in vivo myelination (Bacallao & Monje, 2013; Ghidinelli et al, 2017; Jessen et al, 1991). Recently, we have demonstrated that heat shock protein 90 (Hsp90) stabilizes ErbB2 and plays an important role in nuclear translocation of Grb2‐associated binder 1 (Gab1)/extracellular signal‐regulated kinase (ERK) during cAMP‐induced SC differentiation (Han et al, 2019). Many investigators have studied the role of mitogen‐activated protein kinase/ERK (MAPK/ERK) pathway and phosphoinositide 3‐kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) in SC differentiation and myelination.…”