[Shuttling from the extracellular matrix to the nucleus]

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Extracellular enzymes, including matrix metalloproteinases and lysyl oxidase, are increasingly recognized for intracellular functions.
• Proteoglycans and collagen fragments have also been found within the nucleus, suggesting diverse extracellular protein roles.

Purpose of the Study:

• To explore the nuclear translocation of extracellular proteins.
• To investigate the potential roles of these proteins as nuclear proteases and transcription factors.
• To highlight the underexplored mechanisms and physiological significance of extracellular proteins in the nucleus.

Main Methods:

• Literature review and synthesis of existing research on extracellular protein nuclear import.
• Analysis of studies identifying extracellular enzymes and proteoglycans in nuclear compartments.
• Discussion of potential molecular mechanisms, such as nuclear localizing sequences.

Main Results:

• Several extracellular enzymes (matrix metalloproteinases, lysyl oxidase) and proteoglycans (syndecans, collagen XVIII fragments) are found in the nucleus.
• These nuclear proteins may function as proteases and transcription factors, influencing gene expression and apoptosis.
• Nuclear import is likely facilitated by specific protein sequences.

Conclusions:

• The nuclear presence of extracellular proteins suggests novel regulatory functions beyond their extracellular roles.
• Understanding the mechanisms and in vivo functions of nuclear extracellular proteins is crucial for comprehending cellular processes.
• Further investigation is warranted to elucidate the physiopathological contexts and biological significance of this phenomenon.