Cytoskeletal Protein 4.1G Is Essential for the Primary Ciliogenesis and Osteoblast Differentiation in Bone Formation.

The primary cilium is a hair-like immotile organelle with specific membrane receptors, including the receptor of Hedgehog signaling, smoothened. The cilium organized in preosteoblasts promotes differentiation of the cells into osteoblasts (osteoblast differentiation) by mediating Hedgehog signaling to achieve bone formation. Notably, 4.

Activity of Adenylyl Cyclase Type 6 Is Suppressed by Direct Binding of the Cytoskeletal Protein 4.1G.

The G protein-coupled receptor (GPCR) signaling pathways mediated by trimeric G proteins have been extensively elucidated, but their associated regulatory mechanisms remain unclear. Parathyroid hormone (PTH)/PTH-related protein receptor (PTHR) is a GPCR coupled with G and G G activates adenylyl cyclases (ACs), which produces cAMP to regulate various cell fates. We previously showed that cell surface expression of PTHR was increased by its direct interaction with a subcortical cytoskeletal protein, 4.

Interaction of PICK1 with C-terminus of growth hormone-releasing hormone receptor (GHRHR) modulates trafficking and signal transduction of human GHRHR.

Release of growth hormone (GH) from the somatotroph is regulated by binding GH-releasing hormone (GHRH) to its cognate receptor (GHRHR), one of the members of the G protein-coupled receptor (GPCR) superfamily. Proteins bound to the carboxy (C)-terminus of GPCR have been reported to regulate intracellular trafficking and function of the receptor; however, no functionally significant protein associated with GHRHR has been reported. We have identified a protein interacting with C-kinase 1 (PICK1) as a binding partner of GHRHR.

Suppression of adenylyl cyclase-mediated cAMP production by plasma membrane associated cytoskeletal protein 4.1G.

It has been shown lately that activity of G protein-coupled receptors (GPCRs) is regulated by an array of proteins binding to carboxy (C)-terminus of GPCRs. Proteins of 4.1 family are subsets of subcortical cytoskeletal proteins and are known to stabilize cellular structures and proteins at the plasma membrane.

The hydrophobic amino acids in putative helix 8 in carboxy-terminus of histamine H(3) receptor are involved in receptor-G-protein coupling.

Functional roles of putative helix 8 in the carboxy-terminal tail of the human histamine H(3) receptor were investigated using deleted and alanine-substituted mutant receptors. While the deletion of the carboxy-terminal tail did not decrease the total expression level, surface expression, or ligand binding affinity, the agonist-stimulated cAMP response, [((35))S] GTPγS binding, and MAPK activation were totally abolished. The receptor lacking the carboxy-terminal tail also failed to respond to an inverse agonist, thioperamide, suggesting that the carboxy-terminal tail is involved in the regulation of receptor activity by changing G-protein coupling with the receptor.

Vezatin, a potential target for ADP-ribosylation factor 6, regulates the dendritic formation of hippocampal neurons.

ADP-ribosylation factor 6 (ARF6) is a small GTPase that regulates neuronal morphogenesis processes such as axonal, dendritic, and spine formation possibly through the actin cytoskeleton and membrane trafficking. In an attempt to define the molecular mechanisms that regulate neuronal morphogenesis by ARF6, we identified vezatin as a novel binding partner of active GTP-bound ARF6 using yeast two-hybrid screening. Vezatin was able to bind specifically to GTP-ARF6 among the ARF family.

Agonist-induced internalization of histamine H2 receptor and activation of extracellular signal-regulated kinases are dynamin-dependent.

Histamine H2 receptor (H2R) is a member of G protein-coupled receptor family. Agonist stimulation of H2R results in several cellular events including activation of adenylate cyclase and phospholipase C, desensitization of the receptor, activation of extracellular signal-regulated kinases ERK1/2, and receptor endocytosis. In this study, we identified a GTPase dynamin as a binding partner of H2R.

CLIC4 interacts with histamine H3 receptor and enhances the receptor cell surface expression.

Histamine H3 receptor (H3R), one of G protein-coupled receptors (GPCRs), has been known to regulate neurotransmitter release negatively in central and peripheral nervous systems. Recently, a variety of intracellular proteins have been identified to interact with carboxy (C)-termini of GPCRs, and control their intracellular trafficking and signal transduction efficiencies. Screening for such proteins that interact with the C-terminus of H3R resulted in identification of one of the chloride intracellular channel (CLIC) proteins, CLIC4.

IQ-ArfGEF/BRAG1 is a guanine nucleotide exchange factor for Arf6 that interacts with PSD-95 at postsynaptic density of excitatory synapses.

ADP ribosylation factor 6 (Arf6) is a small GTPase that regulates dendritic differentiation possibly through the organization of actin cytoskeleton and membrane traffic. Here, we characterized IQ-ArfGEF/BRAG1, a guanine nucleotide exchange factor (GEF) for Arf6, in the mouse brain. In vivo Arf pull down assay demonstrated that IQ-ArfGEF/BRAG1 activated Arf6 more potently than Arf1.

Low expression of cell-surface thromboxane A2 receptor beta-isoform through the negative regulation of its membrane traffic by proteasomes.

Human thromboxane A(2) receptor (TP) consists of two alternatively spliced isoforms, TP alpha and TP beta, which differ in their cytoplasmic tails. To examine the functional difference between TP alpha and TP beta, we searched proteins bound to C termini of TP isoforms by a yeast two-hybrid system, and found that proteasome subunit alpha 7 and proteasome activator PA28 gamma interacted potently with the C terminus of TP beta. The binding of TP beta with alpha 7 and PA28 gamma was confirmed by co-immunoprecipitation and pull-down assays.

Somatodendritic localization of EFA6A, a guanine nucleotide exchange factor for ADP-ribosylation factor 6, and its possible interaction with alpha-actinin in dendritic spines.

EFA6A is a member of the guanine nucleotide exchange factors that can specifically activate ADP ribosylation factor 6 (ARF6). In this study, we identified alpha-actinin-1 as a possible interacting protein with EFA6A by the yeast two-hybrid screening with its C-terminal region as bait. The central region of alpha-actinin-1 containing a part of spectrin repeat 1 and spectrin repeats 2-3 is responsible for this interaction.

Recent advances in molecular pharmacology of the histamine systems: roles of C-terminal tails of histamine receptors.

G-protein-coupled receptors (GPCR) represent a large and diverse superfamily of integral membrane proteins to which histamine receptors belong. Increasing numbers of proteins have been identified to interact with the C-termini of GPCRs. These interactions are implicated in targeting, trafficking, and fine-tuning of signaling of GPCRs.

Increase in cell-surface localization of parathyroid hormone receptor by cytoskeletal protein 4.1G.

The cell-surface localization of GPCRs (G-protein-coupled receptors) has emerged as one of critical factors of the GPCR-mediated signal transduction. It has been reported that the C-termini of GPCRs contain the sequences for sorting the receptors to cell surface. In the present study, we have searched for proteins that interact with the C-terminus of PTH (parathyroid hormone)/PTH-related protein receptor (PTHR) by using the yeast two-hybrid system, and identified a cytoskeletal protein 4.

PTH/PTH-related protein receptor interacts directly with Tctex-1 through its COOH terminus.

COOH-terminal cytoplasmic domains of G protein-coupled receptors (GPCRs) have been shown to carry determinants that control their cell surface localization, internalization, and recycling. In attempts to seek cellular proteins that mediate these processes of PTH/PTH-related protein receptor (PTHR), one of the class B GPCRs, we have found that Tctex-1, a 14kDa light chain of cytoplasmic dynein motor complex, interacts with the COOH-terminal tail of the receptor. A 34-amino-acid stretch of the receptor responsible for binding to Tctex-1 has a bipartite structure consisting of a motif previously implicated in binding of some proteins to Tctex-1 and a putative new consensus sequence.