Search

Bacterial photoactivated adenylyl cyclase (bPAC) has been widely used in signal transduction research. However, due to its low two-photon absorption, bPAC cannot be efficiently activated by two-photon (2P) excitation. Taking advantage of the high two-photon absorption of monomeric teal fluorescent protein 1 (mTFP1), we herein developed 2P-activatable bPAC (2pabPAC), a fusion protein consisting of bPAC and mTFP1. In 2pabPAC, the energy absorbed by mTFP1 excites bPAC by Furster resonance energy transfer (FRET) at ca. 43% efficiency. The light-induced increase in cAMP was monitored by a red-shifted FRET biosensor for PKA. In 3D MDCK cells and mouse liver, PKA was activated at single-cell resolution under a 2P microscope. We found that PKA activation in a single hepatocyte caused PKA activation in neighboring cells, indicating the propagation of PKA activation. Thus, 2pabPAC will provide a versatile platform for controlling the cAMP signaling pathway and investigating cell-to-cell communication in vivo.

Optical dimerizers have been developed to untangle signaling pathways, but they are of limited use in vivo, partly due to their inefficient activation under two-photon (2P) excitation. To overcome this problem, we developed Forster resonance energy transfer (FRET)-assisted photoactivation, or FRAPA. On 2P excitation, mTagBFP2 efficiently absorbs and transfers the energy to the chromophore of CRY2. Based on structure-guided engineering, a chimeric protein with 40% FRET efficiency was developed and named 2P-activatable CRY2, or 2paCRY2. 2paCRY2 was employed to develop a RAF1 activation system named 2paRAF. In three-dimensionally cultured cells expressing 2paRAF, extracellular signal-regulated kinase (ERK) was efficiently activated by 2P excitation at single-cell resolution. Photoactivation of ERK was also accomplished in the epidermal cells of 2paRAF-expressing mice. We further developed an mTFP1-fused LOV domain that exhibits efficient response to 2P excitation. Collectively, FRAPA will pave the way to single-cell optical control of signaling pathways in vivo.

Background Platelet-derived growth factor-C (PDGF-C) has been shown to be involved in several biological processes, such as embryonic development, wound healing and angiogenesis, as well as in diseases including tumor formation and fibrotic diseases. However, its role in fibrosarcoma and embryonic stem (ES) cells has not been elucidated. Methods The expression level of PDGF-C was measured using RT-PCR. The activity of PDGF-C was suppressed using RNA interference or a neutralizing antibody and the effect on cell growth was examined using the WST and soft agar assays. Results In the tumor cell lines studied, the highest level of PDGF-C expression was in human HT1080 fibrosarcoma cells. In ES cells, it was highly expressed in the self-renewal state but not in the differentiated state. PDGF-C knockdown suppressed anchorage-dependent and -independent growth of HT1080 and ES cells. In addition, the suppression of PDGF-C activity by a neutralizing antibody retarded ES cell growth. Conclusion Our results suggest that PDGF-C plays an important role in the proliferation of fibrosarcoma and ES cells.