[Frontiers in Bioscience 6, a25-32, November 1, 2001]

Specific regions of the extracellular domain of dlk, AN EGF-like homeotic protein involved in differentiation, participate in intramolecular interactions

Victoriano Baladrón, María José Ruiz-Hidalgo, Elena Gubina, Ezio Bonvini, and Jorge Laborda

Laboratory of Immunobiology, Division of Monoclonal Antibodies, Center for biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and Methods
3.1. Plasmid constructs
3.2. DNA sequencing
3.3. Bacterial strains
3.4. Yeast two-hybrid methods
4. Results
4.1. Mouse dlk interacts with itself though different regions of its extracellular domain in the yeast two-hybrid system
5. Discussion
6. Acknowledgment
7. References

1. ABSTRACT

The level of expression of dlk, an EGF-like protein possessing six EGF-like repeats in its extracellular region, is critical for 3T3-L1 fibroblasts to differentiate into adipocytes in response to IGF1. The mechanism of action of dlk is not well understood, but its localization on the cell membrane suggests that dlk may function as a receptor, as a ligand or as a regulatory protein modulating the binding, the signaling, or the expression of other molecules involved in cell differentiation and growth. In this work, we demonstrate, by using the Yeast Two-Hybrid system, that dlk interacts with itself through specific regions of its extracellular domain. The strongest interactions were observed between specific EGF-like repeats and between a non EFG-like region where unknown proteases act to generate soluble forms of dlk. These observations suggest that the interaction between two membrane dlk molecules belonging to the same or to different cells, or the interaction between soluble and membrane dlk variants, may be important to regulate dlk function.