Scientists have captured on video the intracellular version of a postal delivery service. Reporting in the journal Biochemical and Biophysical Research Communications (BBRC), bioengineering researchers at UC San Diego published videos of a key message-carrying protein called paxillin moving abruptly from hubs of communication and transportation activity on the cell surface toward the nucleus. Paxillin was labeled with a red fluorescence marker to make it stand out in live cells.
Its amazing to us. We thought the cell was so simple, said Shu Chien, the senior author of the BBRC paper and a professor of bioengineering at UCSDs Jacobs School of Engineering. But its really very complex and Im not sure were covering much as yet. We certainly dont know all the interactions among these molecules that bring the cell into action.
Examining living cells through a microscope, Chien and the papers co-author, associate project scientist Ying-Li Hu, filmed red-fluorescence-tagged paxillin molecules traveling from cells outer membrane along green-fluorescence-labeled traces of cytoskeleton. Even without video evidence, scientists have confirmed over the past 10 years that higher organisms use paxillin as a transmitter of locomotion and gene-expression signals from several classes of growth-factor receptors to the nucleus.
Cancer researchers are eager to understand paxillins many interactions because their malfunctions have been linked to a variety of cancers, tumor metastasis, and other disease processes. Tumor-causing versions of signaling molecules may attach to paxillin and disturb the normal adhesion and growth factor signaling steps required for controlled proliferation and cell growth. For example, human papilloma virus, which can cause cervical cancer, makes a protein that binds to paxillin and that interaction may contribute to the carcinogenic potential of the sexually transmitted virus.