Nuclear membrane protein Lem2 regulates nuclear size through membrane flow.

Area of Science:

• Cell Biology
• Molecular Biology
• Organelle Dynamics

Background:

• Nuclear size is proportional to cell size across diverse cell types.
• Mechanisms governing nuclear size determination are not fully understood.
• Inner nuclear membrane proteins play a role in nuclear envelope structure and function.

Purpose of the Study:

• Investigate the role of fission yeast inner nuclear membrane proteins in nuclear size determination.
• Identify proteins that act as barriers to membrane flow within the nuclear envelope.
• Elucidate the mechanisms linking nuclear size to cell size and membrane content.

Main Methods:

• Fission yeast as a model organism.
• Genetic manipulation of inner nuclear membrane proteins (Lem2, Lnp1).
• Analysis of membrane flow dynamics and nuclear envelope integrity.
• Microscopy and biochemical assays to assess nuclear size and membrane transport.

Main Results:

• Lem2 acts as a primary barrier to membrane flow between the nucleus and the cellular membrane system.
• Lem2 deletion leads to altered membrane flow and nuclear size.
• The endoplasmic reticulum protein Lnp1 functions as a secondary barrier, compensating for Lem2 loss.
• Nuclear size is maintained in proportion to cellular membrane content.

Conclusions:

• Lem2 and Lnp1 are key regulators of nuclear size by controlling membrane flow.
• The interplay between these proteins ensures nuclear size scales with cell size.
• These regulatory principles may extend to other eukaryotic organelles.