Inter-organelle contacts facilitate communication between organelles and impact fundamental cellular functions. Investigations into the molecular mechanisms of inter-organelle tethering are still in the early stages, and we are just beginning to appreciate the number and variety of inter-organelle tethers that exist. We have used budding yeast as a model polarized cell system to understanding how cells establish, maintain, and alter contacts between organelles at the right time and place to impact a wide array of cellular functions. The mitochondria-ER-cortex anchor (MECA) tethers mitochondria to the plasma membrane at sites of cortical ER and is required for proper mitochondrial distribution. We find that Num1, the main component of MECA, adopts an extended, polarized conformation in clusters at the cortex with the N-terminal coiled-coil domain (Num1CC) proximal to mitochondria. Num1CC can interact directly with phospholipid membranes and has a preference for cardiolipin, a mitochondrial-specific lipid. The Num1CC-mitochondria interaction is critical for MECA’s tethering function and proper mitochondrial morphology. We find that the assembly of MECA requires mitochondria and that mitochondria-assembled MECA clusters serve as cortical attachment sites for dynein during mitotic spindle positioning. We also find that disrupting the mitochondria-dependent assembly of MECA leads to defects in dynein-mediated spindle positioning. Finally, we find that the ability of Num1 to directly bind mitochondrial membranes and the mitochondria-dependent assembly of Num1 are conserved from budding yeast to fission yeast. This work suggests a fundamental mechanism for inter-organelle tethering through organelle specific lipid binding domains and provides insight into how the regulated assembly of a contact site integrates the positioning and inheritance of two essential organelles. Overall, these findings expand our knowledge of organelle contact site function and contribute to the understanding of conserved mitochondrial tethering mechanisms.

Creator

• Kraft, Lauren Michele

DOI

• https://doi.org/10.21985/n2-wq45-fm86

Subject

• Biology
• Cellular biology

Language

• en

Alternate Identifier

• etdadmin_upload_626904
• http://dissertations.umi.com/northwestern:14460

Keyword

• mitochondria
• membrane contact sites

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright