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Pneumocystis carinii STE11, an HMG-box protein, is phosphorylated by the mitogen activated protein kinase PCM

Pawan K Vohra1, Veenu Puri, Theodore J Kottom

  • 1Thoracic Diseases Research Unit, 826 Stabile Building, Division of Pulmonary, Critical Care and Internal Medicine, Department of Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA.

Gene
|August 12, 2003
PubMed

Insights

Researchers identified a STE11 homologue in Pneumocystis carinii, named PCSTE11, which interacts with the PCM mitogen-activated protein kinase (MAPK) pathway. This finding advances understanding of fungal mating regulation and pathogenicity mechanisms.

Area of Science:

  • Molecular Biology
  • Mycology
  • Biochemistry

Background:

  • Mitogen-activated protein kinase (MAPK) pathways regulate crucial cellular processes in fungi, including mating, by controlling gene transcription.
  • In fungi, transcriptional activators like STE11 and STE12 are key components of these pathways, influencing sexual development, filamentous growth, and pathogenicity.
  • The opportunistic fungus Pneumocystis carinii possesses a MAPK pathway involved in mating, with a previously identified MAPK named PCM.

Purpose of the Study:

  • To identify downstream molecules interacting with the PCM kinase in Pneumocystis carinii.
  • To clone and characterize a homologue of the STE11 transcriptional activator in P. carinii.
  • To investigate the association of the identified STE11 homologue with the P. carinii MAPK cascade.

Main Methods:

  • Cloning of a STE11 homologue (PCSTE11) from P. carinii.
  • Bioinformatic analysis to determine protein characteristics and homology.
  • Expression and purification of a His-tag fusion protein of PCSTE11 using nickel affinity chromatography.
  • In vitro phosphorylation assays using purified PCM kinase and PCSTE11 protein.

Main Results:

  • A P. carinii STE11 homologue, PCSTE11, was successfully cloned, featuring a 1.5 kb open-reading frame encoding a 56 kDa protein.
  • PCSTE11 exhibited the greatest homology (52%) to Schizosaccharomyces pombe STE11.
  • Phosphorylation of purified PCSTE11 by the PCM kinase confirmed PCSTE11's association with the MAPK cascade in P. carinii.

Conclusions:

  • PCSTE11 is a functional component of the pheromone-activated MAPK pathway in Pneumocystis carinii.
  • This study provides initial evidence for the downstream signaling molecules involved in the PCM kinase pathway.
  • The findings contribute to understanding the molecular mechanisms governing mating and potentially pathogenicity in P. carinii.

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