Heh2/Man1 may be an evolutionarily conserved sensor of NPC assembly state

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Integral membrane proteins of the Lap2-emerin-MAN1 (LEM) family are crucial for nuclear envelope integrity.
• The biochemical interactions governing LEM protein function, particularly with the nuclear pore complex (NPC), are not well understood.

Purpose of the Study:

• To investigate the interaction network of Heh2/Man1, an inner nuclear membrane (INM) protein, with nuclear pore complex (NPC) components.
• To elucidate the domains responsible for Heh2/Man1 targeting to the INM and its stable interaction with the NPC.
• To understand the functional consequences of disrupting Heh2/Man1-NPC interactions.

Main Methods:

• Investigated protein-protein interactions between Heh2/Man1 and NPC scaffold components in yeasts.
• Utilized domain deletion analysis to identify regions of Heh2/Man1 critical for INM targeting and NPC binding.
• Observed the effects of Heh2/Man1 interaction disruption on NPC organization and integrity through genetic manipulation (knockouts).

Main Results:

• Heh2/Man1 interacts with major scaffold components of the NPC, specifically the inner ring complex (IRC), in yeasts.
• A C-terminal winged helix (WH) domain mediates stable NPC interactions, distinct from the N-terminal domain required for INM targeting.
• Deletion of the Heh2 WH domain causes NPC clustering, and NPC association is disrupted by the absence of outer ring nucleoporins, indicating dependence on NPC structural integrity.

Conclusions:

• Heh2/Man1's interaction with the NPC is regulated by distinct domains, decoupling INM localization from NPC binding.
• Heh2/Man1 functions as a sensor of NPC assembly state, potentially playing a role in NPC quality control and segregation during cell division.