Category: Lab Notes: Cell Biology

The heat‑shock response (HSR) is a conserved cellular defence pathway that protects the proteome under stress. By activating HSF1 and inducing heat‑shock proteins, cells stabilise protein folding, prevent aggregation and restore proteostasis during proteotoxic conditions.

The oxidative stress response is a cellular defence system that neutralises reactive oxygen species (ROS) and restores redox balance. Through antioxidant enzymes, Nrf2‑mediated transcription, mitochondrial regulation and damage‑repair pathways, cells protect themselves from oxidative injury and maintain homeostasis.

Cellular stress responses are adaptive defence mechanisms that protect cells from environmental, metabolic and proteotoxic stress. By activating heat‑shock proteins, unfolded protein responses, antioxidant pathways and autophagy, cells restore homeostasis and maintain functional integrity under adverse conditions.

Protein quality control (PQC) is a cellular surveillance system that preserves proteome integrity by monitoring protein folding, repairing misfolded proteins and eliminating damaged or aggregated species. Through coordinated action of chaperones, the ubiquitin–proteasome system and autophagy, PQC protects cells from proteotoxic stress and maintains homeostasis.

Aurora C kinase is a germ‑cell‑enriched member of the Chromosomal Passenger Complex that safeguards meiotic chromosome segregation. By regulating kinetochore–microtubule interactions and cytokinesis, Aurora C ensures gamete quality and genomic stability. Its dysregulation contributes to infertility and tumour progression.

Aurora A kinase is a key regulator of centrosome maturation and spindle assembly. By controlling microtubule dynamics, centrosome separation and chromosome alignment, Aurora A ensures accurate mitotic progression. Its frequent overexpression in cancer highlights its importance in genomic stability and tumour development.

The kinetochore is a dynamic protein complex assembled on centromeric chromatin that binds spindle microtubules, generates tension and ensures accurate chromosome segregation. Through coordinated interactions with Aurora B kinase and spindle checkpoint signalling, the kinetochore maintains mitotic fidelity and prevents aneuploidy.

The spindle assembly checkpoint (SAC) is a mitotic surveillance system that prevents premature anaphase onset by monitoring kinetochore–microtubule attachment and tension. Through coordinated action with Aurora B kinase and the Chromosomal Passenger Complex, the SAC ensures accurate chromosome segregation and protects cells from aneuploidy.

Aurora B kinase is the catalytic core of the Chromosomal Passenger Complex, ensuring accurate chromosome segregation, correcting kinetochore–microtubule attachment errors and coordinating cytokinesis. Its central role in mitotic fidelity and frequent dysregulation in cancer make Aurora B a major therapeutic target.

Borealin (CDCA8) is the structural stabiliser of the Chromosomal Passenger Complex. By anchoring Aurora B, INCENP and Survivin to centromeres and guiding CPC relocation to the spindle midzone, Borealin ensures accurate chromosome segregation and successful cytokinesis.

TRIM5α is a specialised antiviral ubiquitin ligase that recognises retroviral capsids, assembles K63‑linked ubiquitin chains and promotes autophagic degradation. Its tripartite motif and SPRY domain enable potent restriction of retroviruses, making TRIM5α a key factor in innate antiviral immunity and retroviral defence.

RIG‑I is a cytosolic pattern‑recognition receptor that detects viral RNA and activates innate immunity. Its CARD domains become exposed and ubiquitinated by TRIM25, enabling RIG‑I to bind MAVS and trigger interferon production. Through this pathway, RIG‑I converts viral RNA detection into a strong antiviral response.

MDA5 is a cytosolic receptor that detects long viral double‑stranded RNA and activates MAVS‑dependent interferon signalling. Its ATP‑driven filament formation enables precise recognition of replicating RNA viruses, while LGP2 stabilises MDA5 filaments to ensure accurate antiviral responses.

The IAP family consists of intracellular proteins that regulate apoptosis, ubiquitination and immune signalling. Through their BIR domains and RING ligase activity, IAPs control caspase inhibition, NF‑κB activation, inflammasome signalling and tumour cell survival, making them central players in cell biology and cancer research.

The Chromosomal Passenger Complex (CPC) is a dynamic mitotic regulator composed of Aurora B, INCENP, Borealin and Survivin. It ensures accurate chromosome segregation, corrects spindle attachment errors and coordinates cytokinesis, making it essential for genomic stability and highly relevant in cancer biology.