Publication Date

2011

Document Type

Honors Thesis

Department

Biochemistry

Keywords

Mitogen-activated protein kinases, Myogenesis, Mice-Genetics, Mice-Muscles, ERK, p38, JNK

Abstract

Mitogen Activated Protein Kinases (MAPKs) are a conserved family of enzymes that form distinct signaling cascades. MAPKs play a vital role in the organism, responding to growth factors and chemical and physical stresses by phosphorylating cytoplasmic proteins, thereby initiating short term changes or activating specific transcription factors which initiate long term cellular changes (Chang and Karin 2001; Widegren et al., 2000). There are three specifically regulated MAP kinases: extracellular signal-related kinases (ERK 1/2/5), p38 proteins (p38α/β/γ/δ)) and c-Jun amino-terminal kinases (JNK1/2/3). JNK and p38 can be induced by cytokines and are associated with inflammation and apoptosis induction and regulation (Cwalina, 2006; Chang and Karin 2001). ERKs are activated predominantly by growth factors and as a result regulate cell growth and promote hypertrophy (Chang and Karin 2001). Limited research exists which tracks the expression, phosphorylation and subsequent activation of all four differentially regulated MAPK pathways throughout myogenesis. The present research sought to determine the expression, phosphorylation and activation of five MAPKs: ERK1, ERK2, p38Ф±, JNK2 and ERK5, throughout C2C12 murine myogenesis. Myogenesis is the process by which muscle cells proliferate and later differentiate from mononucleated myoblasts to myofibrils. The process of myogenesis is modeled in vitro with the C2C12 cell line where samples were taken at three different time points myoblasts (day 0 (DO) from differentiating medium step down), early myotubes (D4) and late myotubes (D10). To determine that the C2C12 cell line underwent myogenesis, two proteins PCNA and cyclin D1 whose expression are linked to the cell cycle were utilized. As myoblasts progressed to myotubes there was a significant decrease in the amount of both PCNA and cyclin D1. Furthermore throughout myogenesis, ERK1 and ERK2 activation (phosphorylation/expression) increased significantly while p38α activation had no significant change and JNK2 and ERK5 activation decreased significantly. The results indicate that ERK1 and ERK2 activation must be essential for myoblast maturation to early and late myotubes.

Language

English

Comments

vii, 87 p. : col. ill. Honors Project-Smith College, Northampton, Mass., 2011. Includes bibliographical references (p. 73-87)

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