Intracellular transport

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Intracellular transport is the movement of

Eukaryotic cells transport packets of components to particular intracellular locations by attaching them to molecular motors that haul them along microtubules and actin filaments. Since intracellular transport heavily relies on microtubules for movement, the components of the cytoskeleton play a vital role in trafficking vesicles between organelles and the plasma membrane by providing mechanical support. Through this pathway, it is possible to facilitate the movement of essential molecules such as membrane‐bounded vesicles and organelles, mRNA
, and chromosomes.

Intracellular transport between the Golgi apparatus and the endoplasmic reticulum

Intracellular transport is unique to eukaryotic cells because they possess organelles enclosed in membranes that need to be mediated for exchange of cargo to take place.

lysosomal enzymes are transferred specifically to the golgi apparatus
and not to another part of the cell which could lead to deleterious effects.

Fusion

Small membrane bound vesicles responsible for transporting proteins from one organelle to another are commonly found in endocytic and

secretory pathways. Vesicles bud from their donor organelle and release the contents of their vesicle by a fusion event in a particular target organelle.[4]: 634  The endoplasmic reticulum serves as a channel that proteins will pass through bound for their final destination.[3] Outbound proteins from the endoplasmic reticulum will bud off into transport vesicles that travel along the cell cortex to reach their specific destinations.[3]
Since the ER is the site of protein synthesis, it would serve as the parent organelle, and the cis face of the golgi, where proteins and signals are received, would be the acceptor. In order for the transport vesicle to accurately undergo a fusion event, it must first recognize the correct target membrane then fuse with that membrane.

How SNARE proteins play a role in intracellular transport

SNARE
proteins. SNAREs are small, tail-anchored proteins which are often post-translationally inserted into membranes that are responsible for the fusion event necessary for vesicles to transport between organelles in the cytosol. There are two forms of SNARES, the t-SNARE and v-SNARE, which fit together similar to a lock and key. The t-SNAREs function by binding to the membranes of the target organelles, while the v-SNAREs function by binding to the vesicle membranes.

Role of endocytosis

Intracellular transport is an overarching category of how cells obtain nutrients and signals. One very well understood form of intracellular transport is known as endocytosis. Endocytosis is defined as the uptake of material by the invagination of the plasma membrane.[4] More specifically, eukaryotic cells use endocytosis of the uptake of nutrients, down regulation of growth factor receptors’ and as a mass regulator of the signaling circuit. This method of transport is largely intercellular in lieu of uptake of large particles such as bacteria via phagocytosis in which a cell engulfs a solid particle to form an internal vesicle called a phagosome. However, many of these processes have an intracellular component.

receptor mediated endocytosis
.

Role of microtubules

A cytoplasmic dynein motor bound to a microtubule.
A kinesin molecule bound to a microtubule.

The transport mechanism depends on the material being moved. Intracellular transport that requires quick movement will use an actin-myosin mechanism while more specialized functions require microtubules for transport.

spindle poles by utilizing the dynein motor proteins during anaphase
.

Diseases

By understanding the components and mechanisms of intracellular transport it is possible to see its implication in diseases. Defects encompass improper sorting of cargo into transport carriers, vesicle budding, issues in movement of vesicles along cytoskeletal tracks, and fusion at the target membrane. Since the life cycle of the cell is a highly regulated and important process, if any component goes awry there is the possibility for deleterious effects. If the cell is unable to correctly execute components of the intracellular pathway there is the impending possibility for protein aggregates to form. Growing evidence supports the concept that deficits in axonal transport contributes to pathogenesis in multiple neurodegenerative diseases. It is proposed that protein aggregations due to faulty transport is a leading cause of the development of

Alzheimer’s and dementia.[7]

How microtubules play a role in intracellular transport

On the other hand, targeting the intracellular transport processes of these motor proteins constitutes the possibility for pharmacological targeting of drugs. By understanding the method in which substances move along neurons or microtubules it is possible to target specific pathways for disease. Currently, many drug companies are aiming to utilize the trajectory of intracellular transport mechanisms to deliver drugs to localized regions and target cells without harming healthy neighboring cells. The potential for this type of treatment in anti-cancer drugs is an exciting, promising area of research.

See also

References

  1. ^
    PMID 28461574
    .
  2. PMID 18946473
    .
  3. ^
    OCLC 1048014962.{{cite book}}: CS1 maint: location missing publisher (link
    )
  4. ^
    ISBN 978-0-7167-3136-8
    .
  5. PMID 26416952
    .
  6. ^ The Cell: A Molecular Approach.
  7. PMID 16730956
    .
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