The p38α/β Mitogen-activated Protein Kinases Mediate Recruitment of CREB-binding Protein to Preserve Fast Myosin Heavy Chain IId/x Gene Activity in Myotubes

Abstract

In skeletal muscle, the transformation of fast into slow fiber type is accompanied by shifts in fiber type-specific gene expression that includes down-regulation of the adult fast fiber myosin heavy chain IId/x (MyHCIId/x) gene. Here, we report that the mitogen-activated protein kinases (MAPKs) p38␣/␤ regulate MyHCIId/x gene expression. Electrical stimulation of rabbit skeletal muscle cells with a slow fiber type activity pattern and treatment of C2C12 myotubes with Ca 2؉ -ionophore inhibited p38␣/␤ MAPKs and reduced fast fiber type MyHC protein expression and promoter activity. Pharmacological inhibition of p38␣/␤ also down-regulated MyHCII gene expression. In controls, binding of the myocyte enhancer factor-2 (MEF-2) isoforms C and D as a heterodimer to a proximal consensus site within the MyHCIId/x promoter and recruitment of a transcriptional coactivator, the CREB-binding protein CBP, were observed. Overexpression of wild type MEF-2C but not of a MEF-2C mutant that cannot be phosphorylated by p38 induced promoter activity. Mutation of the MEF-2-binding site decreased the inducing effect of overexpressed CBP. Inhibition of p38␣/␤ MAPKs abolished CBP binding, whereas enforced induction of p38 by activated MAPK kinase 6 (MKK6EE) enhanced binding of CBP and increased promoter activity. Furthermore, knockdown of endogenous CBP by RNA interference eliminated promoter activation by MEF-2C or MKK6EE. In electrical stimulated and Ca 2؉ -ionophore-treated myotubes, CBP was absent in complex formation at that site. Taken together, the data indicate that p38␣/␤ MAPKs-mediated coactivator recruitment at a proximal MEF-2 site is important for MyHCIId/x gene regulation in skeletal muscle.Skeletal muscle fibers have been classified into fiber types based on their contraction speed, force development, fatigability, and metabolic functions (1). The characteristic fiber types are fast twitch glycolytic (type IID/X and IIB), fast twitch oxidative/glycolytic (type IIA), and slow twitch oxidative (type I/␤). Fast fibers express the IID/X, IIB, or IIA isoform of the myosin heavy chain (MyHC), 3 whereas slow fibers predominantly express the type I/␤ isoform. The functional, biochemical, and morphological differences between fiber types are a consequence of different fiber-specific gene expression patterns. Fibers are characterized by a remarkable plasticity and can be modulated by chronic low frequency electrical stimulation depending on the imposed activity pattern (2). Physiologically, this transformation process in fiber type occurs in response to altered demands, such as increases in muscle activity (3). Fiber type shifts are also observed during aging and disease. The importance of changes in intracellular Ca 2ϩ as a trigger for fiber type transformation has clearly been demonstrated by a Ca 2ϩ -ionophore-induced fast-to-slow transformation in primary skeletal muscle cells (4, 5). The involvement of calcineurin, a Ca 2ϩ -calmodulin-regulated serine/threonine phosphatase, in transducing the Ca 2ϩ -signal into altered gene expre...

Continuous mild heat stress induces differentiation of mammalian myoblasts, shifting fiber type from fast to slow

“…Murgia et al (31) suggested that the Ras-ERK pathway was required for reestablishment of the slow fiber program in a model simulating nerve impulse activity. p38 MAPK has been reported to control MyHC IIx promoter activity in myotubes (27). Our study demonstrated that CMHS did not enhance the activity of either ERK1/2 or p38 MAPK.…”

“…Several studies have shown that MAPKs are involved in the determination of muscle fiber type phenotypes (27,31). It is possible that heat stress affected the phosphorylation of ERK1/2 or p38 MAPK.…”

“…A fast-to-slow fiber-type shift includes pathways that involve the peroxisome proliferator-activated receptor-␣ coactivator (PGC)-1␣ (21), Ras/ERK-1/2 (31), calcineurin (32), and CaMK IV (48). In contrast, p38 MAPK controls the activity of the MyHC IIx promoter in C2C12 mouse myoblasts and primary rabbit skeletal myotubes (27).…”

Improved insulin sensitivity with calorie restriction does not require reduced JNK1/2, p38, or ERK1/2 phosphorylation in skeletal muscle of 9-month-old rats

“…We used DNP-specific immunoreactivity on carbonyl groups as a marker of protein oxidation in protein bands at four different molecular weights (25,28,43, and 67 kDa). We found no difference between the AL and CR groups for this Values are means Ϯ SE; n ϭ 8 -12 muscles per diet group.…”

“…Multiple members of a family of serine-threonine kinases called mitogen-activated protein kinases (MAPKs) can function as negative regulators of insulin sensitivity. Skeletal muscle highly expresses the JNK1 and JNK2 isoforms of c-Jun NH 2 -terminal kinase (6,14), the ERK1 and ERK2 isoforms of extracellular signal-regulated kinase (62), and the p38␣, p38␤, and p38␥ isoforms of p38 MAPK (43,53). Excessive JNK activation has been frequently implicated in the development of insulin resistance (32,34).…”