Hierarchical integration of mitochondrial and nuclear positioning pathways by the Num1 EF hand

Mol Biol Cell. 2022 Feb 1;33(2):ar20. doi: 10.1091/mbc.E21-12-0610-T. Epub 2022 Jan 5.

Abstract

Positioning organelles at the right place and time is critical for their function and inheritance. In budding yeast, mitochondrial and nuclear positioning require the anchoring of mitochondria and dynein to the cell cortex by clusters of Num1. We have previously shown that mitochondria drive the assembly of cortical Num1 clusters, which then serve as anchoring sites for mitochondria and dynein. When mitochondrial inheritance is inhibited, mitochondrial-driven assembly of Num1 in buds is disrupted and defects in dynein-mediated spindle positioning are observed. Using a structure-function approach to dissect the mechanism of mitochondria-dependent dynein anchoring, we found that the EF hand-like motif (EFLM) of Num1 and its ability to bind calcium are required to bias dynein anchoring on mitochondria-associated Num1 clusters. Consistently, when the EFLM is disrupted, we no longer observe defects in dynein activity following inhibition of mitochondrial inheritance. Thus, the Num1 EFLM functions to bias dynein anchoring and activity in nuclear inheritance subsequent to mitochondrial inheritance. We hypothesize that this hierarchical integration of organelle positioning pathways by the Num1 EFLM contributes to the regulated order of organelle inheritance during the cell cycle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • Cytoskeletal Proteins / metabolism*
  • Cytoskeletal Proteins / physiology
  • Dyneins / metabolism
  • EF Hand Motifs / genetics
  • EF Hand Motifs / physiology*
  • Microtubules / metabolism
  • Mitochondria / metabolism
  • Organelles / physiology
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Saccharomyces cerevisiae Proteins / physiology
  • Spindle Apparatus / metabolism

Substances

  • Cytoskeletal Proteins
  • NUM1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Dyneins