Activation of atypical protein kinase Czeta toward TC10 is regulated by high-fat diet and aerobic exercise in skeletal muscle

Abstract

We determined whether sustained aerobic exercise reverses high-fat diet-induced impairments in the c-Cbl associated protein (CAP)/Casitas b-lineage lymphoma (c-Cbl) signaling cascade in rodent skeletal muscle. Sprague-Dawley rats were placed into either control (n = 16) or high-fat-fed (n = 32) diet groups for 4 weeks. During a subsequent 4-week experimental period, 16 high-fat-fed rats remained sedentary, 16 high-fat-fed rats completed 4 weeks of exercise training, and control animals were sedentary and remained on the control diet. After the intervention period, animals were subjected to hind limb perfusions in the presence (n = 8 per group) or absence (n = 8 per group) of insulin. In the plasma membrane fractions, neither high-fat feeding nor exercise training altered adaptor protein with PH and SH2 domains, (APS), c-Cbl, or TC10 protein concentrations. In contrast, CAP protein concentration and insulin-stimulated plasma membrane c-Cbl tyrosine phosphorylation were reduced by high-fat feeding; but exercise training reversed these impairments. Of note was that insulin-stimulated atypical protein kinase Czeta kinase activity toward TC10 was reduced by high-fat feeding but normalized by exercise training. We conclude that sustained (4 weeks) exercise training can reverse high-fat diet-induced impairments on the CAP/c-Cbl pathway in high-fat-fed rodent skeletal muscle. We also provide the first evidence that the CAP/c-Cbl insulin signaling cascade in skeletal muscle may directly interact with components of the classic (phosphoinositide 3-kinase dependent) insulin signaling cascade.

Figure 1

Plasma membrane CAP protein concentration obtained from normal diet, control (CON); high fat diet, control (HF); high fat diet, exercise trained (HFX) animals. *, Significantly different from CON (p<0.05). †, Significantly different from HFX (p<0.05). Values are means ± SE.

Figure 2

(A) Plasma membrane c-Cbl protein concentration, (B) Plasma membrane tyrosine phosphorylation of c-Cbl obtained from normal diet, control (CON); high fat diet, control (HF); high fat diet, exercise trained (HFX) animals. *, Significantly different from CON (p<0.05). †, Significantly different from HFX (p<0.05). §, Significantly different from basal condition (p<0.05). Values are means ± SE.

Figure 3

(A) Plasma membrane APS protein concentration, (B) Plasma membrane Flotillin concentration, (C) Plasma membrane TC10 concentration obtained from normal diet, control (CON); high fat diet, control (HF); high fat diet, exercise trained (HFX) animals. Values are means ± SE.

Figure 4

Plasma membrane aPKCζ/λ kinase activity toward TC10 obtained from normal diet, control (CON); high fat diet, control (HF); high fat diet, exercise trained (HFX) animals. *, Significantly different from CON (p<0.05). †, Significantly different from HFX (p<0.05). §, Significantly different from basal condition (p<0.05). Values are means ± SE.