Nuclear envelope
Nuclear envelope | |
---|---|
Identifiers | |
TH | H1.00.01.2.01001 |
FMA | 63888 |
Anatomical terminology |
The nuclear envelope, also known as the nuclear membrane,
The nuclear envelope consists of two lipid bilayer membranes: an inner nuclear membrane and an outer nuclear membrane.
Structure
The nuclear envelope is made up of two lipid bilayer membranes, an inner nuclear membrane and an outer nuclear membrane. These membranes are connected to each other by nuclear pores. Two sets of intermediate filaments provide support for the nuclear envelope. An internal network forms the nuclear lamina on the inner nuclear membrane.[7] A looser network forms outside to give external support.[4] The actual shape of the nuclear envelope is irregular. It has invaginations and protrusions and can be observed with an electron microscope.
Outer membrane
The outer nuclear membrane also shares a common border with the endoplasmic reticulum.[8] While it is physically linked, the outer nuclear membrane contains proteins found in far higher concentrations than the endoplasmic reticulum.[9] All four nesprin proteins (nuclear envelope spectrin repeat proteins) present in mammals are expressed in the outer nuclear membrane.[10] Nesprin proteins connect cytoskeletal filaments to the nucleoskeleton.[11] Nesprin-mediated connections to the cytoskeleton contribute to nuclear positioning and to the cell’s mechanosensory function.[12] KASH domain proteins of Nesprin-1 and -2 are part of a LINC complex (linker of nucleoskeleton and cytoskeleton) and can bind directly to cystoskeletal components, such as actin filaments, or can bind to proteins in the perinuclear space.[13][14] Nesprin-3 and -4 may play a role in unloading enormous cargo; Nesprin-3 proteins bind plectin and link the nuclear envelope to cytoplasmic intermediate filaments.[15] Nesprin-4 proteins bind the plus end directed motor kinesin-1.[16] The outer nuclear membrane is also involved in development, as it fuses with the inner nuclear membrane to form nuclear pores.[17]
Inner membrane
The inner nuclear membrane encloses the
Mutations in the
Nuclear pores
The nuclear envelope is punctured by around a thousand
Cell division
During the G2 phase of interphase, the nuclear membrane increases its surface area and doubles its number of nuclear pore complexes.[9] In
Breakdown
In mammals, the nuclear membrane can break down within minutes, following a set of steps during the early stages of mitosis. First,
In addition to the breakdown of the nuclear membrane during the prometaphase stage of mitosis, the nuclear membrane also ruptures in migrating mammalian cells during the interphase stage of the cell cycle.[20] This transient rupture is likely caused by nuclear deformation. The rupture is rapidly repaired by a process dependent on "endosomal sorting complexes required for transport" (ESCRT) made up of cytosolic protein complexes.[20] During nuclear membrane rupture events, DNA double-strand breaks occur. Thus the survival of cells migrating through confined environments appears to depend on efficient nuclear envelope and DNA repair machineries.
Aberrant nuclear envelope breakdown has also been observed in laminopathies and in cancer cells leading to mislocalization of cellular proteins, the formation of micronuclei and genomic instability.[21][22][23]
Reformation
Exactly how the nuclear membrane reforms during telophase of mitosis is debated. Two theories exist[9]—
- Vesicle fusion — where vesicles of nuclear membrane fuse together to rebuild the nuclear membrane
- Re-shaping of the endoplasmic reticulum—where the parts of the endoplasmic reticulum containing the absorbed nuclear membrane envelop the nuclear space, reforming a closed membrane.
Origin of the nuclear membrane
A study of the comparative genomics, evolution and origins of the nuclear membrane led to the proposal that the nucleus emerged in the primitive eukaryotic ancestor (the “prekaryote”), and was triggered by the archaeo-bacterial symbiosis.[24] Several ideas have been proposed for the evolutionary origin of the nuclear membrane.[25] These ideas include the invagination of the plasma membrane in a prokaryote ancestor, or the formation of a genuine new membrane system following the establishment of proto-mitochondria in the archaeal host. The adaptive function of the nuclear membrane may have been to serve as a barrier to protect the genome from reactive oxygen species (ROS) produced by the cells' pre-mitochondria.[26][27]
Notes
References
- ^ Georgia State University. "Cell Nucleus and Nuclear Envelope". gsu.edu. Archived from the original on 2018-06-18. Retrieved 2014-01-21.
- ^ "Nuclear membrane". Biology Dictionary. Biology Online. Retrieved 7 December 2012.
- ^ "nuclear membrane". Merriam Webster. Retrieved 7 December 2012.
- ^ ISBN 978-0815340720.
- ^ "Perinuclear space". Dictionary. Biology Online. Retrieved 7 December 2012.
- ISBN 9780125641555.
- PMID 19379495.
- ^ "Chloride channels in the Nuclear membrane" (PDF). Harvard.edu. Archived from the original (PDF) on 2 August 2010. Retrieved 7 December 2012.
- ^ PMID 20300205.
- PMID 20519579.
- PMID 19922864.
- PMID 25787126.
- PMID 16380439.
- PMID 29376050.
- PMID 16330710.
- PMID 19164528.
- PMID 20926687.
- PMID 11406575.
- ISBN 978-0-8153-4106-2.
- ^ S2CID 28544308.
- PMID 22567193.
- PMID 27799497.
- PMID 27697922. Retrieved 24 March 2019.
- PMID 15611647.
- PMID 16242992.
- S2CID 20068849.
- ISBN 978-3-319-65535-2DOI 10.1007/978-3-319-65536-9
External links
- Histology image: 20102loa – Histology Learning System at Boston University
- Animations of nuclear pores and transport through the nuclear envelope Archived 2009-02-07 at the Wayback Machine
- Illustrations of nuclear pores and transport through the nuclear membrane Archived 2009-02-07 at the Wayback Machine
- Nuclear+membrane at the U.S. National Library of Medicine Medical Subject Headings (MeSH)