Journal: bioRxiv

Article Title: Adenylyl cyclases combinatorially integrate opposing dopamine receptor signals

doi: 10.64898/2026.07.10.737756

Figure Lengend Snippet: (A, B). Single-cell dose-response curves for (A) Gαs-coupled DRD1 and (B) Gαi-coupled DRD2 in CHO-K1::cAMPinG1 cells transiently expressing HALO-tagged receptors. DRD2 was stimulated in the presence of 10 µM forskolin to elevate the baseline cAMP level. Cells are binned and colored by their measured surface receptor abundance (arbitrary flow-cytometry units; see color bars). Solid lines represent joint fits of the operational model (R 2 = 0.98 for DRD1; R 2 = 0.97 for DRD2) with binding affinity (Kd) locked to established IUPHAR values (fit values and 95% CIs are provided in ). Data represent per-bin medians, with error bars indicating ±1 SEM across independent replicate dates (n = 4 for DRD1, n = 5 for DRD2). The remaining subtypes (DRD3, DRD4, DRD5) are characterized in Fig. S3. (C, D) DRD1 dopamine dose-response under siRNA knockdown of Gαs at (C) 1 nM and (D) 33 nM siGNAS (ΔGs), overlaid on the wild-type Gαs response, binned by surface DRD1 abundance (colors as in A). Solid lines are the shared-parameter operational-model fit in which only the available transducer pool [Gs] varies per condition ; Gαs depletion right-shifts the curves along the dose axis without lowering the maximal response. (E). Schematic of the modified operational model. Ligand binding ([L]) yields a fractional receptor occupancy (ρ). This fraction is multiplied by the measured surface receptor abundance ([R]) to yield a composite signaling drive (D = [R] · [G] · ρ). The drive is processed through a saturable Hill-type transducer function (S) to compute the final integrated cAMP output (y). Full mathematical derivation is provided in the Supplementary Information. (F). Master-curve collapse across receptor abundances. Plotting the normalized transducer output (S) against the composite signaling drive (D) collapses the variable dose-response families onto a single, invariant master curve for each receptor subtype. This confirms that cellular cAMP responses are governed by the combined drive quantity rather than receptor density or ligand concentration independently.

Article Snippet: For experiments involving Gαi-coupled receptors (DRD2, DRD3, DRD4), adenylyl cyclase was activated with 10 μM forskolin (MedChemExpress, HY-15371) 5 minutes post-dopamine treatment.

Techniques: Single Cell, Expressing, Flow Cytometry, Binding Assay, Knockdown, Modification, Ligand Binding Assay, Concentration Assay

Journal: bioRxiv

Article Title: Adenylyl cyclases combinatorially integrate opposing dopamine receptor signals

doi: 10.64898/2026.07.10.737756

Figure Lengend Snippet: (A–C) Single-cell dose-response curves for (A) Gαo-coupled DRD3, (B) Gαi-coupled DRD4, and (C) Gαs-coupled DRD5 in CHO-K1::cAMPinG1 cells transiently expressing HALO-tagged receptors. The Gαi/o-coupled subtypes (DRD3, DRD4) were stimulated in the presence of 10 µM forskolin to elevate the baseline cAMP level; the Gαs-coupled DRD5 was measured from the unstimulated baseline. Cells are binned and colored by their measured surface receptor abundance (arbitrary flow-cytometry units; see color bar). Solid lines represent fits of the operational model with binding affinity (Kd) locked to established IUPHAR values (fit values and 95% CIs are provided in ). Data represent per-bin medians, with error bars indicating ±1 SEM across independent replicate dates (n = 2 for DRD3, n = 3 for DRD4, n = 4 for DRD5). (A) DRD3 produces no dopamine-evoked cAMP response, because its primary transducer Gαo is not endogenously expressed in CHO-K1 ; it therefore serves as a silent control. (B) DRD4 shows shallow, expression-dependent suppression of the forskolin-elevated baseline (R 2 = 0.91), consistent with DRD4’s canonical preference for Gαo over Gαi. (C) DRD5 shows expression-dependent cAMP stimulation (R 2 = 0.97). These subtypes are reported for completeness of the receptor panel and are not used in any quantitative downstream analysis; the identifiability of their fits is examined in .

Article Snippet: For experiments involving Gαi-coupled receptors (DRD2, DRD3, DRD4), adenylyl cyclase was activated with 10 μM forskolin (MedChemExpress, HY-15371) 5 minutes post-dopamine treatment.

Techniques: Single Cell, Expressing, Flow Cytometry, Binding Assay, Control

Journal: bioRxiv

Article Title: Adenylyl cyclases combinatorially integrate opposing dopamine receptor signals

doi: 10.64898/2026.07.10.737756

Figure Lengend Snippet: (A) Per-receptor scatter of dopamine binding measurements before and after the stringent curation that produced . Each colored point (orange = Gαs-coupled, blue = Gαi-coupled) is one of the 24 measurements retained in the main figure; each light-grey point is a measurement excluded by one or more curation criteria (see Methods and panel B of this figure). All rows that map to one of the five dopamine receptors are included, with descriptions like “D2L”, “D2A”, and “D2long” mapped to DRD2 (long isoform) by an extended description-matching rule applied in this SI figure but not in the main-text curation, in order to expose the full per-receptor scatter that the database contains. n (kept/total): DRD1 = 6/39, DRD5 = 1/2, DRD2 = 5/116, DRD3 = 10/50, DRD4 = 2/21. Solid colored bars, stringent median (matches ); dashed black ticks, unfiltered median across all rows shown. The two medians lie within 0.1 log unit (≈25%) of each other for every receptor that has more than one entry, indicating that the stringent filter narrows the database but does not systematically bias the central tendency. (B) Counts of GtoPdb rows excluded by each curation criterion. Each row is assigned to the first applicable category in the order: functional assay (Assay Type = “F” in GtoPdb; signaling readouts such as cAMP, β-arrestin recruitment, or [ S]GTPγS binding rather than direct ligand binding), species not specified (assay description does not explicitly state the species), non-human species (description names rat, mouse, bovine, dog, or porcine receptor), other / multiple (combinations of the above or unparseable values, value reported as a range, or “unknown origin” phrase in description), unrecognized assay type (Assay Type column does not contain the standard B/F values).

Article Snippet: For experiments involving Gαi-coupled receptors (DRD2, DRD3, DRD4), adenylyl cyclase was activated with 10 μM forskolin (MedChemExpress, HY-15371) 5 minutes post-dopamine treatment.

Techniques: Binding Assay, Produced, Functional Assay, Ligand Binding Assay