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Identification of a chromosome 3p14.3-21.1 gene, APPL, encoding an adaptor molecule that interacts with the
Y Mitsuuchi1, S W Johnson, G Sonoda
1Molecular Oncology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, PA 19111, USA.
Abstract:
AKT2 is a serine/threonine kinase implicated in human ovarian and pancreatic cancers. AKT2 is activated by a variety of growth factors and insulin via phosphatidylinositol 3-kinase (PI3K). However, its normal cellular role is not well understood. To gain insight into the function of AKT2, we performed yeast two-hybrid system to screen for interacting proteins. Using this technique, we identified a novel interactor, designated APPL, which contains a pleckstrin homology (PH) domain, a phosphotyrosine binding (PTB) domain and a leucine zipper, classes of motifs defined in signaling molecules as functional interaction domains with specific targets. The PH domain of APPL shows similarity to those found in GTPase-activating proteins such as oligophrenin-1 and Graf, whereas its PTB domain exhibits homology with CED-6, an adaptor protein that promotes engulfment of apoptotic cells, and IB1, a transactivator of the GLUT2 gene. APPL is highly expressed in skeletal muscle, heart, ovary and pancreas, tissues in which AKT2 mRNA is abundant. APPL interacts with the inactive form of AKT2; moreover, APPL binds to the PI3K catalytic subunit, p110alpha. These data suggest that APPL is an adaptor that may tether inactive AKT2 to p110alpha in the cytoplasm and thereby may expedite recruitment of AKT2 and p110alpha to the cell membrane upon mitogenic stimulation. Furthermore, the APPL gene was mapped to human chromosome 3p14.3-p21.1, where deletions and other rearrangements have often been reported in a variety of tumor types. The identification of APPL may facilitate further analysis of the physiological and oncogenic activities of AKT2.
Insights
Researchers identified APPL, a novel protein interacting with AKT2 (a kinase involved in cancer). APPL may regulate AKT2 localization and function, offering new insights into cancer biology and AKT2 signaling pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- AKT2 is a serine/threonine kinase crucial in cellular signaling pathways.
- AKT2 activation by growth factors and insulin involves phosphatidylinositol 3-kinase (PI3K).
- The precise physiological role of AKT2 remains incompletely understood.
Purpose of the Study:
- To identify novel proteins interacting with AKT2.
- To elucidate the functional role of AKT2 in cellular processes.
- To investigate potential links between AKT2 interactors and cancer biology.
Main Methods:
- Yeast two-hybrid system screening to identify protein interactors.
- Analysis of protein domain structures (PH, PTB, leucine zipper).
- Gene mapping of the novel interactor to human chromosome 3p14.3-p21.1.
Main Results:
- A novel AKT2-interacting protein, APPL, was identified.
- APPL contains domains characteristic of signaling molecules (PH, PTB, leucine zipper).
- APPL interacts with both inactive AKT2 and the PI3K catalytic subunit p110alpha, and is expressed in tissues with high AKT2 abundance.
Conclusions:
- APPL functions as an adaptor protein, potentially tethering inactive AKT2 to p110alpha in the cytoplasm.
- APPL may facilitate the recruitment of AKT2 and p110alpha to the cell membrane upon stimulation.
- The APPL gene's location on chromosome 3p, a region frequently altered in tumors, suggests its potential involvement in oncogenesis.