Tiam1 mediates Rac1 activation and contraction‐induced glucose uptake in skeletal muscle cells

Abstract

Contraction-stimulated glucose uptake in skeletal muscle requires Rac1, but the molecular mechanism of its activation is not fully understood. Treadmill running was applied to induce C57BL/6 mouse hind limb skeletal muscle contraction in vivo and electrical pulse stimulation contracted C2C12 myotube cultures in vitro. The protein levels or activities of AMPK or the Rac1-specific GEF, Tiam1, were manipulated by activators, inhibitors, siRNA-mediated knockdown, and adenovirus-mediated expression. Activated Rac1 was detected by a pull-down assay and immunoblotting. Glucose uptake was measured using the 2-NBD-glucose fluorescent analog. Electrical pulse stimulated contraction or treadmill exercise upregulated the expression of Tiam1 in skeletal muscle in an AMPK-dependent manner. Axin1 siRNA-mediated knockdown diminished AMPK activation and upregulation of Tiam1 protein expression by contraction. Tiam1 siRNA-mediated knockdown diminished contraction-induced Rac1 activation, GLUT4 translocation, and glucose uptake. Contraction increased Tiam1 gene expression and serine phosphorylation of Tiam1 protein via AMPK. These findings suggest Tiam1 is part of an AMPK-Tiam1-Rac1 signaling pathway that mediates contraction-stimulated glucose uptake in skeletal muscle cells and tissue.

Kalirin mediates Rac1 activation downstream of calcium/calmodulin‐dependent protein kinase II to stimulate glucose uptake during muscle contraction

“…In that study, we demonstrated that calcium‐induced CaMKII activation was in part responsible for the stimulation of glucose uptake [4]. More recently, we have used EPS of C2C12 myotubes as a model of contraction to better understand the signaling pathways necessary for the stimulation of glucose uptake [18,22–24]. In the present study, we explore in greater detail how EPS‐stimulated glucose uptake involves CaMKII.…”

“…Glucose uptake was detected by measuring 2‐NBDG uptake in C2C12 myotubes as described [18]. After treatments, cells were exposed to 2‐NBDG (30 μM) in glucose‐free DMEM for 1 h at 37 °C, then cells were washed with PBS twice quickly and digested with trypsin followed by centrifugation at 1000 g for 5 min at room temperature.…”

“…Our previous results indicate that contraction upregulates the expression and activity of Tiam1 through AMPK, which in turn activates Rac1 and promotes glucose uptake in skeletal muscle [18]. However, knocking down Tiam1 only partially inhibits contraction‐induced Rac1 activity and glucose uptake, suggesting that Rac1 may also be regulated through alternate pathways, including other Rac1 GEFs [18]. In addition to neurons, Kalirin is expressed in endocrine cells, liver, heart, and skeletal muscle [19].…”

Zkscan3 affects erythroblast development by regulating the transcriptional activity of GATA1 and KLF1 in mice

“…Tiam1 expression was significantly increased upon Zkscan3 knockout and Zkscan3 was found to bind Tam1 promoter both in vitro and in vivo. Tiam1 is a Rac1-specific guanine nucleotide exchange factor that selectively activates Rac1 (Yue et al 2021 ). It has been reported that Tiam1 participates in cytoskeleton rearrangement, cell migration, and mobility (Zhu et al 2014 ; Izumi et al 2019 ; Payapilly et al 2021 ).…”

Rho GTPases in Skeletal Muscle Development and Homeostasis

“…The Rho GEF Plekhg4 has been shown to promote Rac1 activation in this process [ 119 ]. Rac1 and the Rho GEFs Tiam1 and Kalirin have also been shown to mediate muscle glucose uptake in response to other stimuli [ 120 , 121 , 122 , 123 , 124 ]. It has also been posited that the RhoA–ROCK1 axis can positively influence insulin signaling in muscle and adipose cells through phosphorylation of the insulin receptor substrate 1 [ 125 , 126 , 127 ].…”