CRIP1a inhibits endocytosis of G‐protein coupled receptors activated by endocannabinoids and glutamate by a common molecular mechanism

Abstract

The excitability of the central nervous system depends largely on the surface density of neurotransmitter receptors. The endocannabinoid receptor 1 (CB R) and the metabotropic glutamate receptor mGlu R are expressed pre-synaptically where they reduce glutamate release into the synaptic cleft. Recently, the CB R interacting protein cannabinoid receptor interacting protein 1a (CRIP1a) was identified and characterized to regulate CB R activity in neurons. However, underlying molecular mechanisms are largely unknown. Here, we identified a common mechanism used by CRIP1a to regulate the cell surface density of two different types of G-protein coupled receptors, CB R and mGlu R. Five amino acids within the CB R C-terminus were required and sufficient to reduce constitutive CB R endocytosis by about 72% in the presence of CRIP1a. Interestingly, a similar sequence is present in mGlu R and consistently, endocytosis of mGlu R depended on CRIP1a, as well. Docking analysis and molecular dynamics simulations identified a conserved serine in CB R (S468) and mGlu R (S894) that forms a hydrogen bond with the peptide backbone of CRIP1a at position R82. In contrast to mGlu R, the closely related mGlu R splice-variant carries a lysine (K894) at this position, and indeed, mGlu R endocytosis was not affected by CRIP1a. Chimeric constructs between CB R, mGlu R, and mGlu R underline the role of the identified five CRIP1a sensitive amino acids. In summary, we suggest that CRIP1a negatively regulates endocytosis of two different G-protein coupled receptor types, CB R and mGlu R.

Protein Interactors and Trafficking Pathways That Regulate the Cannabinoid Type 1 Receptor (CB1R)

“…Five amino acids in the very distal carboxy terminus of CB1R are necessary for CRIP1a binding: D467, T468, S469, A472, and L473 (Mascia et al, 2017) and, interestingly, a similar motif present in the metabotropic glutamate receptor mGlu8a also binds CRIP1a (Mascia et al, 2017).…”

Tat-Cannabinoid Receptor Interacting Protein Reduces Ischemia-Induced Neuronal Damage and Its Possible Relationship with 14-3-3η

“…Presynaptic calcium entry is necessary for neurotransmitter release, and it is well known that CB1R activity inhibits presynaptic calcium channels. CRIP1a interacts with CB1R, suppressing the internalization of CB1R, which is essential for limiting glutamate release into the synaptic cleft [38]. The inhibition of internalization is caused by competing for β-arrestin [39,40], and it has been also reported that CRIP1a delivers newly synthesized CB1Rs to the presynaptic membrane without exogenous agonists of CB1R [41].…”

The C-terminal Helix 9 motif regulates cannabinoid receptor type 1 trafficking and surface expression

“…SGIP1, a protein linked to clathrin-mediated endocytosis, prevents internalisation of activated CB1R (Hajkova et al, 2016). Similarly, cannabinoid receptor interacting protein 1a (CRIP1a) reduces constitutive CB1R internalisation (Mascia et al, 2017) by competing with β-Arrestin binding (Blume et al, 2017).…”