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The Ccz1-Mon1 protein complex is required for the late step of multiple vacuole delivery pathways

Chao-Wen Wang1, Per E Stromhaug, Jun Shima

  • 1Department of Molecular, Cellular, and Developmental Biology, Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109-1048, USA.

The Journal of Biological Chemistry
|October 5, 2002
PubMed

Insights

Mon1 and Ccz1 proteins form a complex essential for transporting proteins to the vacuole. These mutants accumulate precursor proteins in vesicles, revealing their role in membrane trafficking and fusion.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Trafficking

Background:

  • The cytoplasm to vacuole targeting (Cvt) pathway is crucial for delivering aminopeptidase I (Ape1) to the vacuole.
  • Autophagy and pexophagy are degradative pathways that share machinery with the Cvt pathway.
  • Vacuolar import involves complex protein machinery and membrane-trafficking events.

Purpose of the Study:

  • To identify novel proteins involved in the Cvt pathway and other vacuolar import processes.
  • To characterize the function of Mon1 and Ccz1 in protein trafficking to the vacuole.
  • To investigate the interaction and localization of Mon1 and Ccz1.

Main Methods:

  • Gene deletion library screening to identify mutants defective in Ape1 import.
  • Analysis of defects in autophagy, pexophagy, and other vacuolar hydrolase delivery pathways.
  • Biochemical assays, subcellular fractionation, co-immunoprecipitation, and fluorescence microscopy.

Main Results:

  • Mon1 and Ccz1 are essential for the Cvt pathway, autophagy, and pexophagy.
  • Mutants lacking Mon1 or Ccz1 accumulate precursor Ape1 in cytosolic vesicles.
  • Mon1 and Ccz1 function at or before the vesicle fusion step with the vacuole.
  • Mon1 and Ccz1 form a stable complex that associates with the vacuole membrane.

Conclusions:

  • The Ccz1-Mon1 complex plays a critical role in multiple vacuolar import and degradation pathways.
  • This complex is involved in the fusion of transport vesicles with the vacuole.
  • Mon1 and Ccz1 are key regulators of membrane trafficking to the vacuole.

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