Page 35 - Cell biology PDG 2024

There are 3 stages of cell signaling: reception, transduction and
response

Reception

It is the binding of a signaling molecule, or ligand to its receptor. In case
of transmembrane receptors, they are able to transmit information from
outside the cell to the inside because they change conformation when a
specific ligand binds to it

Transduction:

A series of changes in a sequence of different molecules (called a signal
transduction pathway) but sometimes can occur in a single step. The
molecules involved in this are known as relay molecules. During this step
activation of many proteins occur by addition or removal of phosphate
or even the release of other small molecules or ions that can act as
messengers. The amplification of the signal is one of the benefits to this
multiple step sequence.

Response:

It is the final stage of cell signaling. This response can be any cellular
activity that is present in a body that can take place in the nucleus or in
the cytoplasm of the cell. A majority of signaling pathways control
protein synthesis by turning certain genes on and off in the nucleus

These three steps of cell signaling all ensure that the cell is behaving as
told, at the right time, and in synchronization with other cells.

Cell communication

1) Autocrine signaling: it is the production and secretion of an
extracellular mediator (ligand) by a cell followed by the binding of that
mediator to receptors on the same cell to initiate signal transduction

EX: Binding of IL-1 by receptors on macrophages further activates these
cells leading to the secretion of additional cytokines (including additional
IL-1) thus stimulating itself

In cancer, the tumor cell proliferation may be driven by autocrine
signaling

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