Subzellulärlokalisation

Subzellulärlokalisation refers to the specific location of biomolecules, such as proteins and RNA, within a cell and the mechanisms that determine their residence in particular cellular compartments. The localization of these molecules influences their interactions, stability, activity, and participation in cellular processes, and can be static or dynamic, changing in response to signals or developmental cues.

Proteins are directed to distinct compartments by sorting signals and transport pathways. Common signals include nuclear localization signals for import into the nucleus, nuclear export signals for leaving the nucleus, ER signal peptides that initiate cotranslational import into the endoplasmic reticulum, and retention motifs such as KDEL for the ER. For mitochondria, chloroplasts, and peroxisomes, targeting sequences guide proteins through dedicated import machinery (for example, TOM/TIM complexes in mitochondria and PTS1/PTS2 motifs for peroxisomes). Membrane proteins often contain transmembrane domains that anchor them to membranes and determine their orientation. Kinetic and reversible localization, including protein shuttling between compartments, is common and regulated by signaling pathways and post-translational modifications such as lipidation or phosphorylation.

Methods to study subcellular localisation include fluorescence microscopy with tagged proteins (e.g., GFP fusions), subcellular fractionation followed by proteomics, and proximity labeling. Computational approaches predict localization from sequence motifs and structural features, though experimental validation remains essential.

Subzellulärlokalisation is central to cellular function and disease. Mislocalization can disrupt pathways, contribute to stress responses, and is implicated in cancers, neurodegenerative disorders, and inherited diseases, highlighting the importance of proper protein trafficking and compartmental identity.