Associate editor: S.D. BrainActivity-dependent neuroprotective protein: From gene to drug candidate
Section snippets
Introduction: neuroendocrine regulation and neuroprotection
Neurotrophic and neuroprotective mechanisms modulate developmental processes as well as recovery from acute and chronic neural injuries, aging, and death. The development of the nervous system involves cell migration, differentiation (at the level of the single cell into neurons and glia), pruning, and death of certain cell populations. These processes are not limited to embryonic development but they also appear to occur in the adult brain after acute or chronic injury. Brain plasticity during
Activity-dependent neuroprotective protein discovery and structure
ADNP was originally cloned from P19 mouse carcinoma cells differentiated (in the presence of retinoic acid) into neuroglial cells (Bassan et al., 1999). Subsequently, human ADNP was cloned from a fetal brain cDNA library (Zamostiano et al., 2001). Comparative sequence analysis of these 2 ADNP orthologues indicated 90% identity at the mRNA level, suggesting a very high evolutionary conservation, which also extended to the rat sequence (Sigalov et al., 2000). The deduced protein structure
Function
The hADNP gene was mapped to chromosome 20q12-13.2, a region associated with aggressive tumor growth, frequently amplified in many neoplasias, including breast, bladder, ovarian, pancreatic, and colon cancers. hADNP mRNA is abundantly expressed in distinct normal tissues, and high expression levels were encountered in malignant cells. Down-regulation of ADNP by antisense oligodeoxynucleotides up-regulated the tumor suppressor p53 and reduced the viability of intestinal cancer cells by 90%.
Activity-dependent neuroprotective protein expression in rodents
Northern blot hybridizations have identified a unique 5.5-kb mouse ADNP mRNA in the mouse brain. Further hybridizations have identified ADNP mRNA in rat astrocytes. Comparison of tissues revealed an enrichment in brain-derived structures (hippocampus and cerebellum as well as midbrain and cerebral cortex) and low abundance in the lung, kidney, and intestine with slight increases in the testis. When considering the level of the actin mRNA signal (used as an internal standard), the enrichment in
Activity-dependent neuroprotective protein cellular distribution
The subcellular distribution of ADNP was assessed through cell fractionation, gel electrophoresis, immunoblotting, and immunocytochemistry. An antibody directed to the NAP peptide fragment was used (Furman et al., 2004). To assess antibody specificity, recombinant ADNP was used as a competitive ligand (Steingart & Gozes, 2006). ADNP-like immunoreactivity was found in both the cytoplasmic and in the nuclear cell fractions of astrocytes.
In the nucleus, the primary structure of ADNP contains
Activity-dependent neuroprotective protein/NAPVSIPQ, microtubules, and cellular protection
The original discovery of ADNP identified an 8-amino acid fragment, NAP as a domain in ADNP that confers neuroprotection (Bassan et al., 1999). Further studies identified tubulin as a NAP target for astrocyte (Divinski et al., 2004) and neuronal protection (Divinski et al., 2006). Changes in microtubule organization following incubation with NAP parallel decreases in the relative amount of the hyperphosphorylated the tubulin associated unit (tau) (Gozes & Divinski, 2004). Hyperphosphorylated
NAPVSIPQ
NAP was recently reviewed as a neuroprotective drug candidate (Gozes et al., 2005a). In cell culture, NAP has demonstrated protection against toxicity associated with the beta-amyloid peptide, N-methyl-d-aspartate, electrical blockade, the envelope protein of the AIDS virus, dopamine, H2O2, nutrient starvation and zinc overload. In ex vivo whole embryo cultures, NAP mediated protection from ethanol-induced neural tube defects (Chen et al., 2005). NAP has also provided neuroprotection in animal
Concluding remarks and open questions
Turning a stone in biology and medical research unravels unknown mysteries and discovers new horizons for further research and development. The discovery of ADNP led to the discovery of KIAA0863 (Zamostiano et al., 2001) and the relationship of these 2 family members deserves further attention. As indicated in the Section 2, KIAA0863 and ADNP share structural similarities; however, KIAA0863 does not contain the neuroprotective NAP motif. Therefore, an open question is, does KIAA0863 function as
Note added in Proof
We have recently published a relevant new paper that adds insights to ADNP activities (Mandel et al., in press).
Acknowledgments
This work was supported by the United States–Israel Binational Science Foundation, the Israel Science Foundation, and the Lily and Avraham Gildor Chair for the Investigation of Growth Factors, the Dr. Diana and Zelman Elton (Elbaum) Laboratory for Molecular Neuroendocrinology and Allon Therapeutics, Inc. NAP is in clinical development at Allon Therapeutics Inc. Additional support was obtained from the National Institute of Child Health and Human Development, the National Institute on Aging, and
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