Molecular biology of the neuronal cytoskeleton - Article Example

[Teacher’s Biology Molecular biology of the neuronal cytoskeleton. The cytoskeleton is a key defining component in eukaryotic cells. Most people refer to the cytoskeleton as a single component; however, it is comprised of three fundamental structures (Wayne and Morris, n.d). These include the microtubules, microfilaments and neurofilaments, they have different functions, but maintain interaction with one another (Brady and Kirkpatrick, 1). These fibrous subcomponents are synthesized from the polymerization of certain protein subunits.

They each have different protein subunit compositions which are determined by the cell type or sub domain (Brady and Kirkpatrick, 1). These structures play a fundamental role in maintaining the form of neural and other eukaryotic cells (Lasek, Oblinger and Drake, n.p). The structural elements of the neuronal cytoskeleton are visible via an electron microscope. This paper will analyze each component of the cytoskeleton and its morphological features. Microtubules are comprised of tubuline, a heterodimeric protein consisting of two 50kD subunits.

These are known as alpha and beta, and exist in numerous isometric forms. Beta subunits can further be divided into four types which are Beta 1-4. There have been scientific speculations that the structure difference may have an influence on the composition and relative abundance of each form of beta tubulin (Georgiev, Papaioanou and Glazebrook, n.p). In addition, the properties of assembly are determined by the isotopic composition of Beta tubuline. This depends on the location, which raises the notion that the shapes and forms of neural microtubules are connected with their function.

The walls of the microtubules are comprised of 2D polymers of alpha and beta tubilin dimer which are joined together by longitudinal and lateral bonds (Georgiev, Papaioanou and Glazebrook, n.p). The microtubules in neural cells are more diverse than those in other non-neural cells. Neural microtubules have a variety of modifications Another key class of components of the cytoskeleton is that of actin microfilaments. This is the oldest component and possesses a diverse and complex organization.

It is comprised of 42 k-Da actin monomers that are intertwined into fibrils (Giridharan et. al, n.p). The filaments interact with numerous proteins, and place an important role in the development of neurons. These microfilaments are present in glia and neurons and their function in these areas is widely discussed. They display numerous changes during morphogenesis of neurons. Immature neurons were seen to possess bet and gamma actin, whereas gamma actin is absent in mature cells. The main proteins that interact with actin filaments include sprectrin, a protein of erythrocyte origin which binds actin filaments and ankyrin proteins which are mediators of this process.

The meshwork resulting from these bonds is directly bound to membrane proteins of the plasma membrane. Fimbrin is another protein which plays a role in binding of microfilaments. Microfilaments have multiple roles in the neural cells; these include maintenance of membrane proteins and establishment of cell morphology. They are also mediators of the intracellular interactions with the external environment. They also serve a role in the prevention of organelle interaction with the external environment.

The third component of the cytoskeleton that will be discussed is the intermediate or neurofilament. Neurofilaments are specific for different cells and act as markers for differentiation. They have been classified into 5 according to genetic composition and these genes share homology in the core rod domain. These are tissue specific and the distinctive feature of these proteins is their amino acid sequence and their intron placement. They are the intermediate filaments to neurones which are fully matured.

They are composed of three subunits and are obligate heteropolymers. The subunits include NF-H, NF-M and NF-L. These units have unique carboxyl and amino terminal domains. The subunits migrate spontaneously and anonymously due to extensive phosphorylation of NF-H AND NF-M. Each subunit is coded for by a specific gene. Other proteins that occur in neurons include peripherin, alpha intermexin and nestin. These are mainly active during development. The cytoskeleton plays a key role in the distribution of proteins in the plasma membrane, which is key in the morphological establishment of neurons.

The cytoskeleton mediates the connection between the intracellular environment and the matrix complexes and other cells. The appropriate synthesis, organization and composition of these cells are essential as the form and functions of the cell are dependent on these components. Without these components cellular interaction would be limited and hence result in cell death. Works Cited Giridharan, SS, Rohn, JL, Naslavsky, N, nad Caplan, S. Differential regulation of actin filaments by human MICAL proteins.

Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5870, USA. Georgiev, Danko, Stelios, Papaioanou and James, Glazebrook. “Neuronic system inside neurons: Molecular biology and biophysics of neuronal microtubules”. Kirkpatrick, Laura and Brady, Scott. “Molecular Components of Neuronal Cytoskeleton”. NCBI Bookshelf. BookshelfID: NBK28122. Lasek, Raymond. J., Monica. M. Oblinger, and P. F. Drake. "Molecular biology of neuronal geometry: expression of neurofilament genes influences axonal diameter.

" Cold Spring Harbor symposia on quantitative biology. Vol. 48. Cold Spring Harbor Laboratory Press, 1983. Wayne, Davies and Morris, Brian. “Molecular Biology of the Neuron”. Published to Oxford Scholarship Online: September 2009