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The familial mediterranean fever protein interacts and colocalizes with a putative Golgi transporter
X Chen1, Y Bykhovskaya, N Tidow
1Ahmanson Department of Pediatrics, Steven Spielberg Pediatric Research Center, Medical Genetics Birth Defects Center, and Department of Medicine, Cedars-Sinai Medical Center and UCLA School of Medicine, Los Angeles, California 90048, USA.
Abstract:
The biological function of pyrin, the protein mutated in Familial Mediterranean Fever (FMF), has not been elucidated. Based on sequence homology, a transcription factor activity was proposed for this neutrophil-specific protein. In a yeast two-hybrid assay, neither transcription activation activity nor any self interaction was detected for pyrin. Screening of an expression cDNA library of peripheral blood leukocytes using as bait the carboxyl portion of pyrin (amino acids 557-781), which contains most of the FMF mutations, led to the identification of P/M-IP1 (pyrin/marenostrin interacting protein 1). A splice variant of P/M-IP1, GTC-90, had previously been described as a component of the 13S hetero-oligomeric protein complex that stimulates in vitro Golgi transport. We have now shown that P/M-IP1 colocalizes with pyrin in the perinuclear cytoplasm of Cos-7 cells and that the interaction between these two proteins is impaired by FMF causing mutations in pyrin. These data suggest that, at some stage of its functional pathway, pyrin resides in the cytoplasm and might be involved in, or impacted by, cellular protein sorting by the Golgi apparatus. The data also imply that P/M-IP1 may be involved in the abnormal inflammatory response that occurs in patients with FMF.
Insights
Pyrin, the protein linked to Familial Mediterranean Fever (FMF), interacts with P/M-IP1 in the cytoplasm. Mutations in pyrin disrupt this interaction, suggesting a role in cellular protein sorting and FMF pathogenesis.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The biological function of pyrin, mutated in Familial Mediterranean Fever (FMF), remains unclear.
- Previous hypotheses suggested pyrin acts as a neutrophil-specific transcription factor, but this was not supported by yeast two-hybrid assays.
- FMF is a genetic autoinflammatory disorder characterized by recurrent episodes of fever and inflammation.
Purpose of the Study:
- To elucidate the biological function and cellular localization of pyrin.
- To identify proteins that interact with pyrin, particularly in relation to FMF-associated mutations.
- To investigate the potential role of pyrin-interacting proteins in the pathogenesis of FMF.
Main Methods:
- Yeast two-hybrid assays to assess pyrin's self-interaction and transcription factor activity.
- Screening of a peripheral blood leukocyte cDNA library using the carboxyl portion of pyrin as bait.
- Co-localization studies in Cos-7 cells to examine the cellular localization of pyrin and its interacting partner.
- Analysis of pyrin-P/M-IP1 interaction in the presence of FMF-causing mutations.
Main Results:
- Pyrin does not exhibit transcription activation activity or self-interaction in yeast two-hybrid assays.
- P/M-IP1 (pyrin/marenostrin interacting protein 1) was identified as a pyrin-interacting protein.
- P/M-IP1 colocalizes with pyrin in the perinuclear cytoplasm of Cos-7 cells.
- FMF-causing mutations in pyrin impair its interaction with P/M-IP1.
Conclusions:
- Pyrin localizes to the cytoplasm and may be involved in Golgi-mediated protein sorting.
- The interaction between pyrin and P/M-IP1 is crucial for pyrin's cellular function and is disrupted by FMF mutations.
- P/M-IP1 may play a role in the abnormal inflammatory response observed in Familial Mediterranean Fever.