Prostaglandins Secreted by Senescent Cells Inhibit Myoblast Differentiation via HRas C-terminal Cysteines

*Corresponding author: (e-mail: [e-mail]).

Abstract

Background: An irreversible cell cycle arrest characterizes senescence. Senescent cells secrete a variety of biomolecules as a secretory phenotype (SASP), altering the microenvironment surrounding the senescent cells. Chemotherapy-mediated senescent myoblasts secrete 15 deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), an electrophilic eicosanoid prostaglandin, which inhibits myoblast differentiation via a poorly understood mechanism.

Materials and Methods: We induced senescence in C2C12 mouse myoblasts using Doxorubicin to measure the SASP. We treated myoblasts with 15d-PGJ₂ to study the effect on muscle differentiation and the underlying mechanism. We used site-directed mutants to study the role of HRas C-terminal cysteines in 15d-PGJ₂-mediated inhibition of myoblast differentiation.

Results: We show that 15d-PGJ₂ inhibits the differentiation of myoblasts via activation of the HRas-MAPK pathway. 15d-PGJ₂ covalently modifies HRas at Cysteine 184 to alter the intracellular distribution and activity, which is necessary for 15d-PGJ₂-mediated inhibition of myoblast differentiation. We also show that altered intracellular distribution of constitutively active HRas affects the downstream signaling.

Conclusion: We hypothesize that alteration in the intracellular distribution and preferential activation of the HRas-MAPK pathway in a C-terminal cysteine-dependent manner is a mechanism by which electrophilic eicosanoid prostaglandins inhibit the differentiation of myoblasts. This is a possible mechanism where the accumulation of senescent cells leads to chemotherapy-induced cachexia.