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The inner nuclear membrane protein LAP1 forms a native complex with B-type lamins and partitions with

C Maison1, A Pyrpasopoulou, P A Theodoropoulos

  • 1Department of Basic Sciences, The University of Crete School of Medicine, Heraklion, Greece.

The EMBO Journal
|August 15, 1997
PubMed

Insights

Lamina-associated polypeptide-1 (LAP1) forms complexes with B-type lamins in the nuclear envelope. These LAP1-lamin B complexes associate with mitotic vesicles and spindle microtubules during cell division.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The nuclear envelope is a critical cellular structure regulating molecular transport and maintaining nuclear organization.
  • Integral membrane proteins of the inner nuclear membrane, such as lamina-associated polypeptides (LAP1 and LAP2), play key roles in nuclear structure and function.
  • Understanding the spatial organization and interactions of these proteins is essential for comprehending nuclear envelope dynamics.

Purpose of the Study:

  • To investigate the in situ organization and molecular interactions of lamina-associated polypeptide-1 (LAP1) within the mammalian nuclear envelope.
  • To determine the association of LAP1 with other nuclear envelope components, particularly lamins, during interphase and mitosis.
  • To elucidate the behavior of LAP1 during nuclear envelope breakdown and its relationship with mitotic structures.

Main Methods:

  • Immunofluorescence microscopy to visualize the localization of LAP1 and B-type lamins.
  • Biochemical assays to characterize LAP1-containing complexes.
  • Analysis of protein distribution during mitosis, including nuclear envelope breakdown and association with microtubules.

Main Results:

  • During interphase, LAP1 forms multimeric assemblies in the inner nuclear membrane, specifically associated with B-type lamins.
  • The LAP1-lamin B complex is distinct from LAP2-containing complexes and includes a protein kinase.
  • Upon nuclear envelope breakdown, LAP1 localizes to mitotic vesicles that carry lamin B and co-align with spindle microtubules, differentiating them from LAP2-containing nuclear envelope fragments.

Conclusions:

  • The inner nuclear membrane is organized into discrete territories that house specific integral membrane proteins.
  • LAP1 and its associated proteins undergo differential disassembly during mitosis, highlighting distinct organizational principles within the nuclear envelope.
  • These findings provide insights into the dynamic remodeling of the nuclear envelope during cell division and the roles of integral membrane proteins.

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