Illustration of cell division highlighting RAP55/LSM14 protein on mitotic spindle

Cell Division Secrets: How a Little-Known Protein Could Hold the Key to Cancer Research

Nico Varela in Science & Nature June 2025 • 4 min read.

"Unlocking the mysteries of RAP55/LSM14 and its pivotal role in mitotic spindle assembly could revolutionize our understanding of cell behavior and cancer treatment."

Cell division, a fundamental process of life, relies on the precise choreography of numerous proteins and molecular structures. Among these, microtubules (MTs) stand out as essential components of the cell's cytoskeleton. These cylindrical structures, composed of tubulin, are responsible for maintaining cell shape, transporting cellular material, and, crucially, separating chromosomes during mitosis.

The MAP (Microtubule-Associated Proteins) family, encompassing both large proteins like MAP-1A and smaller components such as tau, plays a crucial role in regulating microtubule function. In this context, a protein known as RAP55/LSM14 has garnered attention for its potential involvement in mitotic spindle formation and stability.

Recent research has shed light on the previously underappreciated role of RAP55/LSM14 in cell division. A groundbreaking study reveals its dynamic localization during mitosis and its impact on the assembly and stability of the mitotic spindle. This discovery suggests new possibilities for understanding cell behavior and exploring potential therapeutic targets.

RAP55/LSM14: A New Player in Mitotic Spindle Assembly

Illustration of cell division highlighting RAP55/LSM14 protein on mitotic spindle

The study, conducted on HeLa cells (a commonly used human cell line in biological research), identified RAP55/LSM14 as a Mitotic Spindle Protein (MSP). Using GFP-tagged proteins, researchers observed the protein's location throughout mitosis, revealing a previously unreported localization pattern. This novel finding challenges existing assumptions about the key players in cell division.

The researchers further demonstrated that depleting RAP55/LSM14 destabilizes spindle assembly, arresting cells in mitosis and triggering various cytoskeletal disorders. This pivotal discovery underscores the importance of RAP55/LSM14 in maintaining the integrity of the mitotic spindle and ensuring proper cell division. Key observations from the study include:

Spindle Instability: Depletion of RAP55/LSM14 leads to compromised spindle assembly.
Cell Cycle Arrest: Cells halt in mitosis, unable to proceed with division.
Cytoskeletal Disruptions: Various disorders arise, indicating a broad impact on cellular structure.
Direct Tubulin Binding: RAP55/LSM14 directly interacts with tubulin, a core component of microtubules.

To understand the mechanism of action, the researchers conducted an "in vitro" assay, revealing that RAP55/LSM14 directly binds to tubulin. This interaction is crucial for stabilizing the mitotic spindle, marking a significant advancement in our understanding of cell division. This direct binding suggests that RAP55/LSM14 acts as a stabilizer, reinforcing the microtubule structures essential for chromosome segregation.

Implications for Cancer Research

The discovery of RAP55/LSM14's critical role in mitotic spindle stability opens exciting new avenues for cancer research. Given that uncontrolled cell division is a hallmark of cancer, targeting RAP55/LSM14 could offer a novel therapeutic strategy. By disrupting the protein's function, it may be possible to selectively inhibit the proliferation of cancer cells, potentially leading to new and more effective treatments.

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This article is based on research published under:

DOI-LINK: 10.18388/abp.2015_1107, Alternate LINK

Title: Localization And Role Of Rap55/Lsm14 In Hela Cells: A New Finding On The Mitotic Spindle Assembly

Subject: General Biochemistry, Genetics and Molecular Biology

Journal: Acta Biochimica Polonica

Publisher: Polskie Towarzystwo Biochemiczne (Polish Biochemical Society)

Authors: Donia Mili, Dane Georgesse, Abderraouf Kenani

Published: 2015-01-01

Everything You Need To Know

What is RAP55/LSM14's role in cell division?

RAP55/LSM14 is a protein identified as a Mitotic Spindle Protein (MSP). Research shows it plays a crucial role in the assembly and stability of the mitotic spindle during cell division. It directly binds to tubulin, a core component of microtubules, reinforcing the structures needed for chromosome segregation. Without sufficient RAP55/LSM14, spindle assembly is compromised, cells halt in mitosis, and cytoskeletal disorders arise.

How are microtubules and microtubule-associated proteins related to RAP55/LSM14's function?

Microtubules (MTs) are cylindrical structures made of tubulin, essential for cell shape, intracellular transport, and chromosome separation during mitosis. MAPs, like MAP-1A and tau, regulate microtubule function. RAP55/LSM14 binds directly to tubulin, stabilizing microtubules in the mitotic spindle. Understanding this interaction provides insights into how microtubules are regulated during cell division.

What happens when RAP55/LSM14 is depleted during cell division?

Researchers observed that depleting RAP55/LSM14 in HeLa cells destabilized spindle assembly, arrested cells in mitosis, and triggered cytoskeletal disorders. This indicates that RAP55/LSM14 is essential for the integrity of the mitotic spindle and proper cell division. Further research demonstrated that RAP55/LSM14 directly binds to tubulin, a core component of microtubules which suggests that RAP55/LSM14 acts as a stabilizer.

How could the discovery of RAP55/LSM14's role in mitotic spindle stability impact cancer research and treatment?

Targeting RAP55/LSM14 could offer a novel therapeutic strategy by disrupting its function, inhibiting the proliferation of cancer cells, potentially leading to new and more effective treatments. However, further research is needed to determine the best way to target the protein without harming healthy cells. More studies have to be done to understand which specific cancers will be impacted, and the long-term effects of inhibiting RAP55/LSM14.

What methods were used to discover the function of RAP55/LSM14, and what further research is needed?

The study used GFP-tagged proteins in HeLa cells to observe the location of RAP55/LSM14 throughout mitosis, revealing a previously unreported localization pattern. Researchers conducted an "in vitro" assay, to understand the mechanism of action. This revealed that RAP55/LSM14 directly binds to tubulin. Further research needs to explore how RAP55/LSM14 interacts with other proteins and structures involved in cell division. Also, investigating its regulation and modification during the cell cycle will provide a more complete understanding.