Related Experiment Video
Updated: Jul 23, 2026
09:31
Heterokaryon Technique for Analysis of Cell Type-specific Localization
Published on: March 11, 2011
The role of IFNgamma nuclear localization sequence in intracellular function
C M Iqbal Ahmed1, Marjorie A Burkhart, Mustafa G Mujtaba
1Department of Microbiology and Cell Science, University of Florida, PO Box 110700, Gainesville, FL 32611-0700, USA. ahmed1@ufl.edu
Journal of Cell Science
|June 12, 2003
Summary
Intracellular interferon gamma (IFNγ) exhibits biological activity, including antiviral effects and MHC class I upregulation. This activity depends on its nuclear localization sequence (NLS) and involves STAT1α activation and nuclear translocation.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Intracellular interferon gamma (IFNγ) demonstrates biological activity comparable to extracellular IFNγ.
- The mechanisms underlying intracellular IFNγ's biological effects require elucidation.
Purpose of the Study:
- To investigate the mechanisms by which intracellular IFNγ mediates biological effects.
- To determine the role of the nuclear localization sequence (NLS) in intracellular IFNγ activity.
Main Methods:
- Adenoviral vectors were used to express wild-type and NLS-mutant non-secreted human IFNγ.
- Biological responses, STAT1α activation, and protein complex formation were analyzed.
- Receptor-mediated endocytosis of extracellular IFNγ was examined.
Main Results:
- Non-secreted wild-type IFNγ induced antiviral activity and MHC class I upregulation.
- An NLS-mutant IFNγ lacked biological activity, indicating the NLS is crucial.
- Intracellular IFNγ activated STAT1α and promoted nuclear translocation of IFNγ, IFNGR1, and STAT1α.
- A complex of IFNγ-IFNGR1-STAT1α was identified in cellular extracts.
- Extracellular IFNγ exhibited intracellular signaling activity dependent on NLS via receptor-mediated endocytosis.
Conclusions:
- Intracellular IFNγ possesses significant biological activity mediated by its NLS.
- The NLS is essential for IFNγ's intracellular signaling and biological functions.
- Extracellular IFNγ can exert intracellular effects through receptor-mediated endocytosis and NLS-dependent mechanisms.
Related Concept Videos
01:34Nuclear Protein Sorting
Nuclear protein sorting is the selective trafficking of histones, polymerases, gene regulatory proteins into the nucleus and exporting RNAs and ribosomes to the cytosol. It is a tightly controlled process that regulates gene expression within a cell.
Proteins targeted to the nucleus carry nuclear localization signals or NLS recognized by import receptors in the cytosol. Similarly, proteins with nuclear export signals are recognized by export receptors. Import and export receptors are...
Proteins targeted to the nucleus carry nuclear localization signals or NLS recognized by import receptors in the cytosol. Similarly, proteins with nuclear export signals are recognized by export receptors. Import and export receptors are...
01:46Nuclear Localization Signals and Import
Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of 2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
01:42Nuclear Export
The nucleus restricts several proteins within and allows others to pass. The restricted proteins possess a nuclear retention sequence or NRS, anchoring them to the nuclear lamins and preventing their transport to the cytosol. The non-restricted proteins, after their synthesis, are transported to their site of action, such as the cytosol or other organelles, with the help of nuclear export signals or NES.
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
01:45Regulation of Nuclear Protein Sorting
Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
02:26NF-κB-dependent Signaling Pathway
The transcription factor NF-κB was discovered in 1986 in the lab of Nobel laureate Professor David Baltimore, for its interaction with the immunoglobulin light chain enhancer in B-cells. After more than three decades of study, it is now evident that NF-κB regulates the expression of over 100 genes. Most of these genes play an essential role in the innate and adaptive immune responses as well as the inflammatory responses of animals.
NF-κB-dependent Signaling Mechanism
The heterodimer of NF-κB...
NF-κB-dependent Signaling Mechanism
The heterodimer of NF-κB...
01:17Intracellular Signaling Affects Focal Adhesions
Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Some...