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Amplifying Signals via Second Messengers

Amplifying Signals via Second Messengers

Many receptor binding ligands are hydrophilic; they do not cross the cell membrane but bind to cell-surface receptors. Thus, their message must be relayed by second messengers present in the cell cytoplasm. There are several second messenger pathways, each with its own way of relaying information. For example, the G protein-coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol pathway is active when the receptor induces...

What are Second Messengers?

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Because many receptor binding ligands are hydrophilic, they do not cross the cell membrane and thus their message must be relayed to a second messenger on the inside. There are several second messenger pathways, each with their own way of relaying information. G-protein coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol path is active when the receptor induces phospholipase C to hydrolyze the phospholipid,...

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Updated: Dec 16, 2025

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation

Published on: August 30, 2017

Upconversion nanoparticles as intracellular pH messengers.

Evaline S Tsai¹, Fadwa Joud², Lisa M Wiesholler³

¹Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Dr., Cambridge, CB3 0AS, UK.

Analytical and Bioanalytical Chemistry

|July 3, 2020

Summary

This summary is machine-generated.

Upconversion nanoparticles (UCNPs) modified with pH-sensitive dyes can image cellular pH in real-time. These nanoparticles are taken up by cells via clathrin-mediated endocytosis, enabling intracellular pH monitoring.

Keywords:

Endocytosis Fluorescence microscopy Intracellular Nanosensors Upconversion nanoparticles pH measurements

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Area of Science:

Nanotechnology
Cell Biology
Biomedical Imaging

Background:

Upconversion nanoparticles (UCNPs) offer advantages for cellular imaging, overcoming limitations like photobleaching and autofluorescence.
UCNPs can be functionalized with pH-sensitive components for intracellular sensing applications.

Purpose of the Study:

To evaluate the performance of UCNPs modified with a pH-sensitive dye (pHAb) for intracellular pH measurement.
To investigate the cellular uptake mechanism of these UCNP-pHAb conjugates.

Main Methods:

UCNPs were coated with polyethylene imine (PEI) and functionalized with a pH-sensitive dye (pHAb).
Förster resonance energy transfer (FRET) efficiencies were measured at varying pH levels.
UCNP-pHAb uptake and localization were studied in human neuroblastoma SH-SY5Y cells using fluorescence microscopy and colocalization with lysosome markers.
Cellular uptake pathways were elucidated using drug inhibitors of endocytosis (CPZ and NYS).

Main Results:

The UCNP-pHAb conjugate exhibited a sigmoidal pH response curve with an apparent pKa of ~5.1.
UCNP-pHAb nanoparticles were observed to colocalize with lysosomes within SH-SY5Y cells.
Nanoparticle uptake was found to be primarily mediated by clathrin-mediated endocytosis.

Conclusions:

pH indicator-modified UCNPs (UCNP-pHAb) are capable of reporting pH within SH-SY5Y cells.
The study elucidates the mechanism of UCNP-pHAb cellular internalization, highlighting clathrin-mediated endocytosis.