DCX

Fig1. Major human paralogs of DCX. (Abiola A Ayanlaja, 2017)

What is DCX protein?

DCX (doublecortin) gene is a protein coding gene which situated on the long arm of chromosome X at locus Xq23. This gene encodes a member of the doublecortin family. The protein encoded by this gene is a cytoplasmic protein and contains two doublecortin domains, which bind microtubules. In the developing cortex, cortical neurons must migrate over long distances to reach the site of their final differentiation. The encoded protein appears to direct neuronal migration by regulating the organization and stability of microtubules. In addition, the encoded protein interacts with LIS1, the regulatory gamma subunit of platelet activating factor acetylhydrolase, and this interaction is important to proper microtubule function in the developing cortex. The DCX protein is consisted of 365 amino acids and its molecular mass is approximately 40.6 kDa.

What is the function of DCX protein?

The DCX protein binds to microtubules, which are part of the cell's structural framework known as the cytoskeleton. This binding promotes the stability of microtubules, which are essential for the neuron's movement and positioning. Furthermore, DCX is expressed in migrating neurons throughout the central and peripheral nervous system during both embryonic and postnatal development. It coassembles with brain microtubules and stimulates the polymerization of purified tubulin, indicating that it likely directs neuronal migration by regulating the organization and stability of microtubules.

DCX Related Signaling Pathway

The DCX protein interacts with microtubules to regulate their stability and dynamics, which are critical for neuronal migration. The AKT signaling pathway plays an important role in cell survival, proliferation, and migration. Studies have shown that activation of the AKT signaling pathway can promote the proliferation and differentiation of neural stem cells, and the expression of DCX, as a marker of neuronal migration, may be regulated by this pathway. Activation of the JNK/c-Jun signaling pathway is associated with induction of DCX expression, which may help repair the cytoskeleton and protect neurons.

DCX Related Diseases

Subcortical Band Heterotopia (SBH) is an abnormal development of the cerebral cortex caused by insufficient neuronal migration. Individuals with SBH often have severe brain developmental deformities and may be accompanied by epilepsy and cognitive impairment. X-linked lissencephaly with or without mental retardation (XLIS) is a genetic disorder caused by mutations in the DCX gene, characterized by a smooth cerebral cortex. Lack of normal gyri and sulci. Abnormal expression or loss of function of the DCX gene has also been linked to a number of other neurodevelopmental disorders that may affect cognitive, language, motor, and other functions.

Bioapplications of DCX

As a drug target, DCX can be used for drug screening and development. In drug development, specific variations of DCX, or proteins with which it interacts, can be used as potential targets to treat certain diseases. DCX recombinant protein can be used as a biomarker to detect and evaluate disease states related to nervous system development, such as epilepsy, cognitive impairment, etc.

Case Study 1: Abiola Abdulrahman Ayanlaja, 2020

Nuclear translocation of several oncogenic proteins have previously been reported, but neither the translocation of doublecortin (DCX) nor the mechanism involved has been studied. DCX is a neuronal microtubule-associated protein (MAP) that is crucial for adult neurogenesis and neuronal migration and has been associated with poor prognosis in gliomas. The researchers probed DCX expression in different grades of glioma tissues and conventional cells via western blotting. Confocal Immunofluorescence was used to detect DCX expression in the cellular compartments, while subcellular fractionation was probed via western blotting. To probe for DCX functions, stable cells expressing high DCX expression or knockdown were generated using CRISPR-Cas9 viral transfection, while plasmid site-directed mutant constructs were used to validate putative nuclear localization sequence (NLS) predicted via conventional algorithms and comparison with classical NLSs. in-silico modeling was performed to validate DCX interactions with import receptors via the selected putative NLS. DCX undergoes nucleocytoplasmic movement via the RanGTPase signaling pathway with an NLS located on the N-terminus between serine47-tyrosine70. This translocation could be stimulated by MARK's phosphorylation of the serine 47 residue flanking the NLS due to aberrant expression of glial cell line-derived neurotrophic factor (GDNF). High expression and nuclear accumulation of DCX improve invasive glioma abilities in-vitro and in-vivo.

Fig1. DCX protein levels as detected by western blotting in non-neoplastic tissues.

Fig2. Pulse shape analysis of U251MG cells expressing DCX mutants compared with the vector showing lower pulse height in DCXNLS2 mutant cells.

Case Study 2: Maryam Moslehi, 2019

Doublecortin X (DCX) plays essential roles in neuronal development via its regulation of cytoskeleton dynamics. This is mediated through direct interactions between its doublecortin (DC) domains (DC1 and DC2) with microtubules (MTs) and indirect association with actin filaments (F-ACT). While the regulatory role of the DCX C-terminus following DC2 has been established, less is known of the possible contributions made by the DCX N-terminus preceding DC1. Here, we assessed the influence of DCX Ser28 within the DCX N-terminus, on the association of DCX with MTs and F-ACT. The researchers compared the cytoskeletal interactions of the DCX S28E phosphomimetic and DCX S28A phospho-resistant mutants and wild-type DCX. Immunoprecipitation and colocalisation analyses indicated increased association of DCX S28E with F-ACT but decreased interaction with MTs, and conversely enhanced DCX S28A association with MTs but decreased association with F-ACT. To evaluate the impact of DCX mutants on cytoskeletal filaments we performed fluorescence recovery after photobleaching (FRAP) studies on SiR-tubulin and β-actin-mCherry and observed comparable tubulin and actin exchange rates in the presence of DCX WT and DCX S28A. However, they observed faster tubulin exchange rates but slower actin exchange rates in the presence of DCX S28E. Moreover, DCX S28E enhanced the association with the actin-binding protein spinophilin (Spn) suggesting the shift to favour association with both F-ACT and Spn in the presence of DCX S28E.

Fig3. Immunoblotting was performed to detect the endogenous α-tubulin and DCX.

Fig4. The time to reach the half-maximal recovery of fluorescence (t1/2) for SiR-tubulin associated with GFP-DCX proteins.

DCX has several biochemical functions, for example, calcium-dependent protein serine/threonine kinase activity,calmodulin binding,calmodulin-dependent protein kinase activity. Some of the functions are cooperated with other proteins, some of the functions could acted by DCX itself. We selected most functions DCX had, and list some proteins which have the same functions with DCX. You can find most of the proteins on our site.

DCX has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with DCX here. Most of them are supplied by our site. Hope this information will be useful for your research of DCX.

GOLGA2;IKZF1;ZBTB5;TRIM27;TRIM23;MEOX1