Sekundärmessengerstoffen

Sekundärmessengerstoffe, also known as second messengers, are intracellular signaling molecules that relay signals received at receptors on the cell surface to target molecules within the cell. They play a crucial role in amplifying and diversifying cellular responses to external stimuli. When a primary messenger, such as a hormone or neurotransmitter, binds to its receptor, it triggers the production or release of one or more second messengers. These molecules then diffuse within the cytoplasm or are localized to specific organelles.

Common examples of second messengers include cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), inositol trisphosphate (IP3), diacylglycerol (DAG), and calcium ions (Ca2+). Each second messenger has specific downstream targets, often enzymes or ion channels, that it activates or inhibits. For instance, cAMP typically activates protein kinase A (PKA), while calcium ions can activate a variety of calcium-binding proteins like calmodulin.

The activation of these downstream targets leads to a cascade of events that ultimately alter cellular function, such as changes in gene expression, metabolism, ion transport, or cell growth. The system of second messengers allows for a highly regulated and amplified response to external signals, enabling cells to adapt to their environment and perform complex physiological functions. This intricate signaling network is fundamental to processes like cell communication, muscle contraction, and memory formation.