Architecture of cannabinoid signaling in mouse retina.
Cannabinoid receptors and their ligands constitute an endogenous signaling system that is found throughout the body, including the eye. This system can be activated by Delta(9)-tetrahydrocannabinol, a major drug of abuse. Cannabinoids offer considerable therapeutic potential in modulating ocular immune and inflammatory responses and in regulating intraocular pressure. The location of cannabinoid receptor 1 (CB(1)) in the retina is known, but recently a constellation of proteins has been identified that produce and break down endocannabinoids (eCBs) and modulate CB(1) function. Localization of these proteins is critical to defining specific cannabinoid signaling circuitry in the retina. Here we show the localization of diacylglycerol lipase-alpha and -beta (DGLalpha/beta), implicated in the production of the eCB 2-arachidonoyl glycerol (2-AG); monoacylglycerol lipase (MGL) and alpha/beta-hydrolase domain 6 (ABHD6), both implicated in the breakdown of 2-AG; cannabinoid receptor-interacting protein 1a (CRIP1a), a protein that may modulate CB(1) function; and fatty acid amide hydrolase (FAAH) and N-acylethanolamine-hydrolyzing acid amidase (NAAA), which have been shown to break down the eCB anandamide and related acyl amides. Our most prominent finding was that DGLalpha is present in postsynaptic type 1 OFF cone bipolar cells juxtaposed to CB(1)-containing cone photoreceptor terminals. CRIP1a is reliably presynaptic to DGLalpha, consistent with a possible role in cannabinoid signaling, and NAAA is restricted to retinal pigment epithelium, whereas DGLbeta is limited to retinal blood vessels. These results taken together with previous anatomical and functional studies define specific cannabinoid circuitry likely to modulate eCB signaling at the first synapse of the retina as well as in the inner plexiform layer.
Hu
Sherry Shu-Jung
SS
The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, USA.
Arnold
Andy
A
Hutchens
Jacqueline M
JM
Radicke
Josh
J
Cravatt
Benjamin F
BF
Wager-Miller
Jim
J
Mackie
Ken
K
Straiker
Alex
A
D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D001808:Blood Vessels / Q000166:cytology / Q000378:metabolism; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D060588:LIM Domain Proteins; D008071:Lipoprotein Lipase / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008994:Monoacylglycerol Lipases / Q000378:metabolism; D043882:Receptors, Cannabinoid / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000033:anatomy & histology / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D063385:Cannabinoid Receptor Modulators; D002352:Carrier Proteins; D005968:Glutamate Decarboxylase; D007527:Isoenzymes; D060588:LIM Domain Proteins; D008071:Lipoprotein Lipase; D008994:Monoacylglycerol Lipases; D043882:Receptors, Cannabinoid; D011993:Recombinant Fusion Proteins; D000099252:Fatty Acid Amide Hydrolases; C489507:Crip1 protein, mouse; C527261:ABHD6 protein, mouse; C402565:glutamate decarboxylase 1