Melanopsin is a retinaldehyde-based, invertebrate-like photopigment [26], [27] involved with mediating many responses to light that require a measure of general environmental irradiance [14], [15], [28], [29], [30] and more recently, the ability of light to modulate sleep [31], [32], [33].
Protein kinases often have a central role in signal transduction pathways and as such mediate many molecular responses within the cells.
Indeed, Gβγ dimers are known to mediate many cellular responses and signaling pathways involved in multiple aspects of cellular function.
On the other hand, in HepG2 cells, the basal mRNA levels of SXR (steroid and xenobiotic receptor) and CAR (constitutive androstane receptor), two xenobiotic sensors that mediate many xenobiotic responses, are the highest among the three cell clines.
Rapid herbivore-induced jasmonic acid (JA) accumulation is known to mediate many induced defense responses in vascular plants, but little is known about how JA bursts are metabolized and modified in response to repeated elicitations, are propagated throughout elicited leaves, or how they directly influence herbivores.
p75NTR is induced in CNS neurons after many types of injury (Kokaia et al., 1998; Roux et al., 1999; Casha et al., 2001; Ramos et al., 2007), and can mediate many different cellular responses, including neuronal apoptosis or survival, and regulation of axonal growth (Rabizadeh et al., 1993; Frade et al., 1996; Maggirwar et al., 1998; Friedman, 2000).
NO, a relatively stable uncharged radical that readily crosses lipid membranes, is a good inter- and intracellular trafficker in mediating many cellular responses (Crow 1997).
The transcriptional complex hypoxia-inducible factor (HIF) has emerged as a key regulator mediating many cellular responses necessary to adapt to changes in oxygen tension (reviewed in Maxwell et al, 2001; Goonewardene et al, 2002; Pugh and Ratcliffe, 2003).
Akt is a downstream effecter molecule of phosphoinositide 3-kinase and is thought to mediate many immune and inflammatory responses.
Many responses mediated by the nervous system are directed toward preserving the status quo, or homeostasis, of the animal.
