Signaling and metabolic properties of fast and slow smooth muscle types from mice

Abstract

This study aims to improve the classification of smooth muscle types to better understand their normal and pathological functional phenotypes. Four different smooth muscle tissues (aorta, muscular arteries, intestine, urinary bladder) with a 5-fold difference in maximal shortening velocity were obtained from mice and classified according to expression of the inserted myosin heavy chain (SMHC-B). Western blotting and quantitative PCR analyses were used to determine 15 metabolic and 8 cell signaling key components in each tissue. The slow muscle type (aorta) with a 12 times lower SMHC-B had 6-fold lower expression of the phosphatase subunit MYPT1, a 7-fold higher expression of Rhokinase 1, and a 3-fold higher expression of the PKC target CPI17, compared to the faster (urinary bladder) smooth muscle. The slow muscle had higher expression of components involved in glucose uptake and glycolysis (type 1 glucose transporter, 3 times; hexokinase, 13 times) and in gluconeogenesis (phosphoenolpyruvate carboxykinase, 43 times), but lower expression of the metabolic sensing AMP-activated kinase, alpha 2 isoform (5 times). The slow type also had higher expression of enzymes involved in lipid metabolism (hormone-sensitive lipase, 10 times; lipoprotein lipase, 13 times; fatty acid synthase, 6 times; type 2 acetyl-coenzyme A carboxylase, 8 times). We present a refined division of smooth muscle into muscle types based on the analysis of contractile, metabolic, and signaling components. Slow compared to fast smooth muscle has a lower expression of the deactivating phosphatase and upregulated Ca²⁺ sensitizing pathways and is more adapted for sustained glucose and lipid metabolism.

Keywords: Contractile kinetics; Energy metabolism; Myosin isoforms; Phasic; Shortening velocity; Tonic.

Fig. 1

Expression of signaling components in smooth muscles with different relative expression of SMHC-B. The data show from left to right: aorta, mesenteric artery, ileum, and urinary bladder, n = 4–8. The Western blot data for the signaling components are given relative to the expression in the urinary bladder. a MYPT1, b PP1β, c PKCα, d CPI17. a Aorta p < 0.05 compared to all other groups, femoral artery p < 0.05 compared to ileum. b, c No significant differences. d Aorta p < 0.05 compared to all other groups. Panels (e) and (f) show Western blots for MYPT1 and ROCK1, respectively, from two separate gels. Equal amounts of protein from aorta (lanes 1, 5), mesenteric artery (lanes 2, 6), intestine (lanes 3, 7), and urinary bladder (lanes 4, 8) were separated. The third lane on each gel (white area) contained another sample not examined in this study

Fig. 2

Expression of signaling components in smooth muscles with different relative expression of SMHC-B. The Western blot data show from left to right: aorta, mesenteric artery, ileum, and urinary bladder, n = 3–8. The data for the signaling components are given relative to the expression in the urinary bladder. a RhoGDI, b RhoA, c ROCK1, d ROCK2. a, b, d No significant differences. c Aorta p < 0.05 compared to all other groups, mesenteric artery p < 0.05 compared to ileum and urinary bladder

Fig. 3

Expression of metabolic components in smooth muscles with different relative expression of SMHC-B. The RT-qPCR data show from left to right: aorta, femoral artery, ileum, and urinary bladder, n = 9–10. a GLUT1, b GLUT4, c PYRK, d HEXO. a Aorta p < 0.05 compared to all other groups, femoral artery p < 0.05 compared to urinary bladder. b Ileum p < 0.05 compared to bladder and aorta, femoral artery p < 0.05 compared to aorta. c No significant differences. d All groups are significantly (p < 0.05) different

Fig. 4

Expression of metabolic components in smooth muscles with different relative expression of SMHC-B. The RT-qPCR data show from left to right: aorta, femoral artery, ileum, and urinary bladder, n = 9–10. a PEPCK, b LDH, c G6PHD, d TFAM, e AMPKα1, f AMPKα2. a Aorta p < 0.05 compared to all other groups, femoral artery p < 0.05 from ileum and urinary bladder. b No significant differences. c Urinary bladder p < 0.05 compared to all other groups. d Ileum p < 0.05 compared to all other groups, aorta p < 0.05 compared to urinary bladder. e Ileum p < 0.05 compared to femoral artery and urinary bladder, aorta p < 0.05 compared to femoral artery and urinary bladder. f Ileum p < 0.05 compared to all other groups, urinary bladder p < 0.05 compared to aorta and femoral artery

Fig. 5

Expression of metabolic components in smooth muscles with different relative expression of SMHC-B. The RT-qPCR data show from left to right: aorta, femoral artery, ileum, and urinary bladder, n = 9–10. a MCD, b HSL, c LPL, d FAS, e ACC2. a Urinary bladder p < 0.05 compared to aorta and ileum. b Aorta and femoral artery p < 0.05 compared to ileum and urinary bladder. c All group significantly (p < 0.05) different. d Aorta and femoral artery p < 0.05 compared to ileum and urinary bladder, ileum p < 0.05 compared to urinary bladder. e Aorta and femoral artery p < 0.05 compared to ileum and urinary bladder