Eukaryotic Transmembrane Signaling

For the Membrane Interface, see
Membrane Interface

For Transmembrane Signaling in General, see
Transmembrane Signaling in General

Because of my surprise at the number of Amphioxus GPCRs, I decided to try and find when GPCRs first appeared in evolution. 

Google found 220,000 hits for "
Eukaryotic GPCRs". 
PubMed found 39 hits for "Eukaryotic GPCRs". 

The Molecular History of Eukaryotic Life (Goog?) 
Good resource.  "Seven transmembrane segment receptors are eukaryotic proteins." "Yeast have only 3 GPCRs: STE2, STE3 and GPR1. These are receptors for pheromone (STE2 and STE3) and a receptor that is induced during starvation. "  "...the fungi have not exploited these useful receptors very much. They seem to be used for mating purposes and for sensing the concentration of glucose in the environment.

The seven transmembrane receptors have a remarkable similarity to bacteriorhodopsin and halorhodopsin. These are a light driven proton pump and a light driven chloride pump from the archaebacteria Halobacterium salinarium (previously named  halobium).

This seems to imply that the GPCRs have their evolutionary roots in the archaea but didn't become full-fledged GPCRs until evolution of the eukaryotes. 

Signaling systems of lower eukaryotes and their evolution 
Only abstract available online.  I got the 132 page PDF through the library. 

Signaling receptome: a genomic and evolutionary perspective (PubMed)    
Only abstract available online.  I got PDF from the library.  Also discussed in
Transmembrane Signaling in General

This article completely ignores prokaryote signaling. 
The single receptor which evolved at the single cell eukaryotic stage is the seven transmembrane (7TM) G-protein coupled receptor (GPCR).  Although the article doesn't give estimates for the total number of all receptors, it does give a breakdown for the five types of GPCRs found in seven genomes.  The totals obtained by adding all five types together are: 

Genome                                         Number of Different GPCRs

Nematode                                               1000 
Fruit Fly                                                     260 
Mosquito                                                   270 
Sea Squirt                                                 210 
Fish                                                            570 
Human                                                       800 
    and from another source - Amphioxus Neurotransmitters   
Amphioxus                                                664  

Eukaryotic vs. prokaryotic chemosensory systems (PubMed) 
Only abstract available online.  I have PDF.