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MRTFA-SRF driven gene expression promotes cellular stiffness by controlling cytoplasmic Ca2+ and K+ levels in cancer cells

ABSTRACT: Cellular stiffness, the inverse of compliance, is a biophysical property of cells that fundamentally impacts homeostatic functions and pathological states and understanding how these properties are controlled can provide novel insights into tissue homeostasis and disease mechanisms. A prominent regulator of cellular stiffness is the filamentous actin (F-actin) cytoskeleton that forms aligned stress fibers during cellular contraction. It has been recently shown that F-actin polymerization and the subsequent cortical stiffening of cancer cells is regulated by the myocardin-related transcription factor A (MRTFA) and this results in dramatic changes in the ability of cancer cells to evade anti-tumor immune surveillance. However, the precise mechanism by which MRTFA regulated cortical stiffness remained unknown. Here, we demonstrate that cancer cell stiffening occurs as a consequence of MRTFA binding to its cofactor serum response factor (SRF). Specifically, MRTFA-SRF promotes the expression of Ca2+ and K+ handling genes and the flux of these ions are critically needed for cortical stiffening. Finally, we show the results of a series of rigorous gain-of-function and loss-of-function studies that reveal the large conductance K+ channel auxiliary subunit, KCNMB1, as an MRTFA-SRF target that regulates cell stiffness and F-actin organization. Collectively, these findings point to previously unrecognized MRTFA-SRF targets in cellular stiffness, including a novel druggable ion channel.

ORGANISM(S): Mus musculus

PROVIDER: GSE273414 | GEO | 2026/01/19

REPOSITORIES: GEO

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Project description:Duchenne muscular dystrophy (DMD) is characterized by impaired cytoskeleton organization, cytosolic calcium handling oxidative stress and mitochondrial dysfunction. This results in progressive and fatal muscle damage, wasting and weakness. The Striated Muscle activator of Rho signalling (STARS) is an actin binding protein that activates the myocardin-related transcription factor-A (MRTFA)/serum response factor (SRF) transcriptional pathway; a pathway that regulates cytoskeletal structure, muscle function, growth and repair. Here we investigated the regulation of several members of the STARS signalling pathway in muscle from patients with DMD and the dystrophin-deficient mdx and dko (utrophin‐ and dystrophin‐null) mice. A reduction in protein levels of STARS, SRF and RHOA, and an increase in MRTFA were observed in quadriceps muscle of patients with DMD. STARS, SRF and MRTFA mRNA levels were also decreased in DMD muscle, while Stars mRNA levels were decreased in mdx tibialis anterior (TA) muscle and Srf and Mrtfa mRNAs were decreased in dko TA muscle. Overexpressing the human STARS (hSTARS) protein in mdx TA muscle increased maximal isometric specific force by 13%. This was not associated with changes in muscle mass, fibre cross-sectional area (CSA), fibre type, centralized nuclei or collagen deposition. Proteomics screening identified 31 upregulated and 22 downregulated proteins or individual peptides that were significantly regulated by hSTARS overexpression. Pathway enrichment analysis indicated that hSTARS overexpression regulated the keratin, NRF2 and oxidative phosphorylation (OXPHOS) pathways. These pathways are impaired in dystrophic muscle and regulate cytoskeleton organization, oxidative stress and mitochondrial energy production; processes that are vital for muscle function. We conclude that increasing the STARS protein in dystrophic muscle improves muscle force production, potentially via its regulation of multiple pathways that positively influence cytoskeletal structure, oxidative stress and energy production.

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MRTFA-SRF driven gene expression promotes cellular stiffness by controlling cytoplasmic Ca2+ and K+ levels in cancer cells

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