Complete open reading frame (C-ORF) technique: rapid and efficient method for obtaining complete protein coding sequences

AEG-1/MTDH/LYRIC, the beginning: initial cloning, structure, expression profile, and regulation of expression

Since its initial identification as a HIV-1-inducible gene in 2002, astrocyte elevated gene-1 (AEG-1), subsequently cloned as metadherin (MTDH) and lysine-rich CEACAM1 coisolated (LYRIC), has emerged over the past 10 years as an important oncogene providing a valuable prognostic marker in patients with various cancers. Recent studies demonstrate that AEG-1/MTDH/LYRIC is a pleiotropic protein that can localize in the cell membrane, cytoplasm, endoplasmic reticulum (ER), nucleus, and nucleolus, and contributes to diverse signaling pathways such as PI3K-AKT, NF-κB, MAPK, and Wnt. In addition to tumorigenesis, this multifunctional protein is implicated in various physiological and pathological processes including development, neurodegeneration, and inflammation. The present review focuses on the discovery of AEG-1/MTDH/LYRIC and conceptualizes areas of future direction for this intriguing gene. We begin by describing how AEG-1, MTDH, and LYRIC were initially identified by different research groups and then discuss AEG-1 structure, functions, localization, and evolution. We conclude with a discussion of the expression profile of AEG-1/MTDH/LYRIC in the context of cancer, neurological disorders, inflammation, and embryogenesis, and discuss how AEG-1/MTDH/LYRIC is regulated. This introductory discussion of AEG-1/MTDH/LYRIC will serve as the basis for the detailed discussions in other chapters of the unique properties of this intriguing molecule.

Astrocyte elevated gene-1: recent insights into a novel gene involved in tumor progression, metastasis and neurodegeneration

Tumor progression and metastasis are complex processes involving intricate interplay among multiple gene products. Astrocyte elevated gene (AEG)-1 was cloned as an human immunodeficiency virus (HIV)-1-inducible and tumor necrosis factor-alpha (TNF-alpha)-inducible transcript in primary human fetal astrocytes (PHFA) by a rapid subtraction hybridization approach. AEG-1 down-regulates the expression of the glutamate transporter EAAT2; thus, it is implicated in glutamate-induced excitotoxic damage to neurons as evident in HIV-associated neurodegeneration. Interestingly, AEG-1 expression is elevated in subsets of breast cancer, glioblastoma multiforme and melanoma cells, and AEG-1 cooperates with Ha-ras to augment the transformed phenotype of normal immortal cells. Moreover, AEG-1 is overexpressed in >95% of human malignant glioma samples when compared with normal human brain. Overexpression of AEG-1 increases and siRNA inhibition of AEG-1 decreases migration and invasion of human glioma cells, respectively. AEG-1 contains a lung-homing domain facilitating breast tumor metastasis to lungs. These findings indicate that AEG-1 might play a pivotal role in the pathogenesis, progression and metastasis of diverse cancers. Our recent observations indicate that AEG-1 exerts its effects by activating the nuclear factor kappa B (NF-kappaB) pathway and AEG-1 is a downstream target of Ha-ras and plays an important role in Ha-ras-mediated tumorigenesis. These provocative findings are intensifying interest in AEG-1 as a crucial regulator of tumor progression and metastasis and as a potential mediator of neurodegeneration. In this review, we discuss the cloning, structure and function(s) of AEG-1 and provide recent insights into the diverse actions and intriguing properties of this molecule.