Gpr63 is a modifier of microcephaly in Ttc21b mouse mutants

Snedeker, John; Gibbons, William J.; Paulding, David; Abdelhamed, Zakia; Prows, Daniel R.; Stottmann, Rolf W.

doi:10.1371/journal.pgen.1008467

Cited by 8 publications

(7 citation statements)

References 51 publications

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“…With a few exceptions (e.g. Gpr88, Gpr161, Gpr63 and EP4 contain LPG motifs in their CTs 27,36 ), the same exact motifs are not present in these other receptors. Still, many of them have similar motifs that could potentially perform the same function (e.g.…”

Section: Discussionmentioning

confidence: 99%

Htr6 and Sstr3 ciliary targeting relies on both IC3 loops and C-terminal tails

Barbeito

Tachibana

Martin-Morales

et al. 2020

Preprint

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G protein-coupled receptors (GPCRs) are the most common pharmacological target in clinical practice. To perform their signaling functions, many GPCRs must accumulate at primary cilia, microtubule-based plasma membrane protrusions that work as cellular antennae. Despite their great importance, the molecular mechanisms underlying GPCR ciliary targeting remain poorly understood. Serotonin receptor 6 (Htr6) and somatostatin receptor 3 (Sstr3) are two brain-enriched ciliary GPCRs controlling cognition and involved in multiple pathologies such as Alzheimer's disease and cancer. We previously showed that the third intracellular loops (IC3s) of Htr6 and Sstr3 contain ciliary targeting sequences (CTSs) that are sufficient to confer ciliary localization to non-ciliary GPCRs. However, these CTSs are dispensable for the ciliary targeting of Htr6 and Sstr3 themselves, suggesting these GPCRs have additional CTSs. Herein, we show that the C-terminal tails of Htr6 and Sstr3 also contain CTSs, which act redundantly with those in the IC3s. Accordingly, simultaneous disruption of CTS1 (IC3) and CTS2 (C-terminal tail) abolishes ciliary targeting of both receptors. Mapping the individual residues required for Htr6 ciliary targeting reveals RKQ and LPG motifs critical for CTS1 and CTS2 function, respectively. In Sstr3, CTS1 function relies on the tandem AP[AS]CQ motifs and a subsequent arginine-rich stretch, whereas CTS2 operation requires the juxtamembrane residues. Furthermore, we shed light on the mechanisms of action of Htr6 CTSs by showing how they regulate binding to Tulp3 and Rabl2, two adapters needed for ciliary GPCR targeting. 3 (IC3s). This was first found for Sstr3 and Htr6 and was later extended to others like Mchr1, Gpr161, Mc4r or Npy2r 9,[20][21][22][23] .For Sstr3 and Htr6, their CTSs were discovered by generating chimeras between these ciliary GPCRs and their non-ciliary relatives Sstr5 and Htr7. After extensive analyses, replacing the IC3s of Sstr5 or Htr7 with those of Sstr3 or Htr6, respectively, was found to suffice for ciliary targeting of the nonciliary receptors. Furthermore, ciliary targeting of these chimeras was abolished by mutating to phenylalanine the first and last residues of Ax[AS]xQ motifs (hereafter referred to as A-Q motifs) present in the IC3s of both Sstr3 and Htr6 20 . In this study, another interesting observation was noted: the reverse pair of chimeras, in which the IC3s of Sstr3 and Htr6 were replaced by those of Sstr5 and Htr7, still accumulated in cilia, indicating that the newly discovered CTSs, albeit sufficient for ciliary targeting of non-ciliary receptors, were dispensable for ciliary targeting of Sstr3 and Htr6 themselves. This suggested, it was also noted, the presence of additional CTSs in these receptors 20 . A subsequent study confirmed that Htr6 IC3 is dispensable for its ciliary targeting 16 .Herein, we report the identification and characterization of those missing CTSs. We show that, for both Sstr3 and Htr6, ciliary targeting occurs as long as either IC3, CT, or both, are pre...

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Section: Discussionmentioning

confidence: 99%

Htr6 and Sstr3 ciliary targeting relies on both IC3 loops and C-terminal tails

Barbeito

Tachibana

Martin-Morales

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Beyond HTR6 orthologs, most known ciliary GPCRs do not have these exact same motifs (not shown). Still, there are exceptions (e.g., GPR88, GPR161, GPR63, and PTGER4 all have LPG motifs in their CTs ( 34 , 42 )), and most ciliary GPCRs do have similar motifs that may potentially perform the same function (e.g., many have RK or similar motifs in their IC3s). However, for these analyses to be more meaningful, we would need to know which residue substitutions preserve or disrupt CTS function at each position within the motif.…”

Section: Discussionmentioning

confidence: 99%

HTR6 and SSTR3 ciliary targeting relies on both IC3 loops and C-terminal tails

et al. 2020

View full text Add to dashboard Cite

G protein-coupled receptors (GPCRs) are the most common pharmacological target in human clinical practice. To perform their functions, many GPCRs must accumulate inside primary cilia, microtubule-based plasma membrane protrusions working as cellular antennae. Nevertheless, the molecular mechanisms underlying GPCR ciliary targeting remain poorly understood. Serotonin receptor 6 (HTR6) and somatostatin receptor 3 (SSTR3) are two brain-enriched ciliary GPCRs involved in cognition and pathologies such as Alzheimer’s disease and cancer. Although the third intracellular loops (IC3) of HTR6 and SSTR3 suffice to target non-ciliary GPCRs to cilia, these IC3s are dispensable for ciliary targeting of HTR6 and SSTR3 themselves, suggesting these GPCRs contain additional ciliary targeting sequences (CTSs). Herein, we discover and characterize novel CTSs in HTR6 and SSTR3 C-terminal tails (CT). These CT-CTSs (CTS2) act redundantly with IC3-CTSs (CTS1), each being sufficient for ciliary targeting. In HTR6, RKQ and LPG motifs are critical for CTS1 and CTS2 function, respectively, whereas in SSTR3 these roles are mostly fulfilled by AP[AS]CQ motifs in IC3 and juxtamembrane residues in CT. Furthermore, we shed light on how these CTSs promote ciliary targeting by modulating binding to ciliary trafficking adapters TULP3 and RABL2.

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“…Studies using murine models on inbred background have provided valuable information as to the factors that contribute to phenotypic variability ( Nadeau, 2001 ; Hamilton and Yu, 2012 ; Kousi and Katsanis, 2015 ). Numerous studies have reported different levels of phenotypic severity on various inbred backgrounds ( Jones et al, 2008 ), as utilization of these strains can more readily identify genetic modifiers via SNP array, GigaMuga and quantitative trait locus (QTL) analysis ( Morgan et al, 2015 ; Snedeker et al, 2019 ). Studies such as these have been instrumental in identifying genetic modifiers that can contribute to increasing the variability of phenotypic presentations in ciliopathies.…”

Section: Discussionmentioning

confidence: 99%

Centriolar Protein C2cd3 Is Required for Craniofacial Development

Chang

Brown

Yang

et al. 2021

Front. Cell Dev. Biol.

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The primary cilium is a ubiquitous, microtubule-based cellular organelle. Primary cilia dysfunction results in a group of disorders termed ciliopathies. C2 domain containing 3 centriole elongation regulator (C2cd3), encodes a centriolar protein essential for ciliogenesis. Mutations in human C2CD3 are associated with the human ciliopathy Oral-Facial-Digital syndrome type 14 (OFD14). In order to better understand the etiology of ciliopathies including OFD14, we generated numerous murine models targeting C2cd3. Initial analysis revealed several tissue-specific isoforms of C2cd3, and while the loss of C2cd3 has previously been reported to result in exencephaly, tight mesencephalic flexure, pericardial edema, abnormal heart looping and a twisted body axis, further analysis revealed that genetic background may also contribute to phenotypic variation. Additional analyses of a conditional allelic series targeting C-terminal PKC-C2 domains or the N-terminal C2CD3N-C2 domain of C2cd3 revealed a variable degree of phenotypic severity, suggesting that while the N-terminal C2CD3N-C2 domain was critical for early embryonic development as a whole, there was also a craniofacial specific role for the C2CD3N-C2 domains. Together, through generation of novel models and evaluation of C2cd3 expression, these data provide valuable insight into mechanisms of pathology for craniofacial ciliopathies that can be further explored in the future.

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Gpr63 is a modifier of microcephaly in Ttc21b mouse mutants

Cited by 8 publications

References 51 publications

Htr6 and Sstr3 ciliary targeting relies on both IC3 loops and C-terminal tails

Htr6 and Sstr3 ciliary targeting relies on both IC3 loops and C-terminal tails

HTR6 and SSTR3 ciliary targeting relies on both IC3 loops and C-terminal tails

Centriolar Protein C2cd3 Is Required for Craniofacial Development

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