Gravin

The emergence of recurrent, metastatic prostate cancer following the failure of androgen-deprivation therapy represents the lethal phenotype of this disease. However, little is known regarding the genes and pathways that regulate this metastatic process, and moreover, it is unclear whether metastasis is an early or late event. The individual genetic loss of the metastasis suppressor, SSeCKS/Gravin/AKAP12 or Rb, genes that are downregulated or deleted in human prostate cancer, results in prostatic hyperplasia...

PURPOSE: : Colorectal cancer (CRC) is a common and potentially lethal disease. A number of genetic aberrations is known to take place in colorectal carcinogenesis, which leads to progressive alteration of normal mechanisms controlling cell growth. A-kinase-anchoring protein 12 (AKAP12) plays a role in cell proliferation, angiogenesis and cytoskeletal remodeling. The purpose of this study was to demonstrate the role of the AKAP12 gene expression in CRC patients and to determine its relationship (if any) with prognosis...

Gravin, an A-kinase anchoring protein, targets protein kinase A (PKA), protein kinase C (PKC), calcineurin and other signaling molecules to the beta2-adrenergic receptor (β2-AR). Gravin mediates desensitization/resensitization of the receptor by facilitating its phosphorylation by PKA and PKC. The role of gravin in β-AR mediated regulation of cardiac function is unclear. The purpose of this study was to determine the effect of acute β-AR stimulation on cardiac contractility in mice lacking functional gravin...

Hypoxia has been widely implicated in many pathological conditions, including those associated with inflammation and tumorigenesis. A number of recent studies have implicated hypoxia in the control of vasculogenesis and permeability, the basis for which is not fully understood. Here we examine the transcriptional regulation of angiogenesis and permeability by hypoxia in endothelial cells. Guided by a global profiling approach in cultured endothelial cells, these studies revealed the selective induction of human gravin (protein kinase A anchoring protein 12) by hypoxia...

A-Kinase Anchoring Proteins (AKAPs) direct the flow of cellular information by positioning multiprotein signaling complexes into proximity with effector proteins. However, certain AKAPs are not stationary but can undergo spatiotemporal redistribution in response to stimuli. Gravin, a 300kD AKAP that intersects with a diverse signaling array, is localized to the plasma membrane but has been shown to translocate to the cytosol following the elevation of intracellular calcium ([Ca(2+)]i). Despite the potential for gravin redistribution to impact multiple signaling pathways, the dynamics of this event remain poorly understood...

Acute leukemias are caused by genetic and epigenetic mechanisms involving tumor suppressor genes and oncogenes. Aberrant DNA methylation patterns are the most frequent molecular alterations detected in acute myeloid leukemia (AML). Gravin is down-regulated in several solid tumors and is implicated in tumorigenesis. To explore its role in the molecular pathogenesis and its possible prognostic importance in AML, we have evaluated the expression levels of the gravin gene in 83 acute myeloid leukemia patients as compared with controls using quantitative real-time polymerase chain reaction (qRT-PCR)...

A kinase-anchoring proteins (AKAPs) organize compartmentalized pools of protein kinase A (PKA) to enable localized signaling events within neurons. However, it is unclear which of the many expressed AKAPs in neurons target PKA to signaling complexes important for long-lasting forms of synaptic plasticity and memory storage. In the forebrain, the anchoring protein gravin recruits a signaling complex containing PKA, PKC, calmodulin, and PDE4D (phosphodiesterase 4D) to the β2-adrenergic receptor. Here, we show that mice lacking the α-isoform of gravin have deficits in PKA-dependent long-lasting forms of hippocampal synaptic plasticity including β2-adrenergic receptor-mediated plasticity, and selective impairments of long-term memory storage...

The mitogenic and second-messenger signals that promote cell proliferation often proceed through multienzyme complexes. The kinase-anchoring protein Gravin integrates cAMP and calcium/phospholipid signals at the plasma membrane by sequestering protein kinases A and C with G protein-coupled receptors. In this report we define a role for Gravin as a temporal organizer of phosphorylation-dependent protein-protein interactions during mitosis. Mass spectrometry, molecular, and cellular approaches show that CDK1/Cyclin B1 phosphorylates Gravin on threonine 766 to prime the recruitment of the polo-like kinase Plk1 at defined phases of mitosis...

Cellular dynamics are controlled by key signaling molecules such as cAMP-dependent protein kinase (PKA) and protein kinase C (PKC). AKAP12/SSeCKS/Gravin (AKAP12) is a scaffold protein for PKA and PKC which controls actin-cytoskeleton reorganization in a spatiotemporal manner. AKAP12 also acts as a tumor suppressor which regulates cell-cycle progression and inhibits Src-mediated oncogenic signaling and cytoskeletal pathways. Reexpression of AKAP12 causes cell flattening, reorganization of the actin cytoskeleton, and the production of normalized focal adhesion structures...

Metastatic cell migration and invasion are regulated by altered adhesion-mediated signaling to the actin-based cytoskeleton via activated Src-FAK complexes. Src-suppressed C-kinase substrate (SSeCKS, the rodent orthologue of human Gravin/AKAP12), whose expression is downregulated by oncogenic Src and in many human cancers, antagonizes oncogenic Src pathways including those driving neovascularization at metastatic sites, metastatic cell motility and invasiveness. This is likely manifested through its function as a scaffolder of F-actin and signaling proteins such as cyclins, calmodulin, protein kinase C and A...

Scaffolding proteins such as SSeCKS/Gravin/AKAP12 ("AKAP12") are thought to control oncogenic signaling pathways by regulating key mediators in a spatiotemporal manner. The downregulation of AKAP12 in many human cancers, often associated with promoter hypermethylation, or the loss of its locus at 6q24-25.2, correlates with progression to malignancy and metastasis. The forced re-expression of AKAP12 in cancer cell lines suppresses in vitro parameters of oncogenic growth, invasiveness, and cell motility through its ability to scaffold protein kinase C (PKC), F-actin, cyclins, Src, and phosphoinositides, and possibly through additional scaffolding domains for PKA, calmodulin, β1,4-galactosyltransferase-polypeptide-1, β2-adrenergic receptors, and cAMP-specific 3',5'-cyclic phosphodiesterase 4D...

A-kinase anchoring proteins (AKAPs) have emerged as important regulatory molecules that can compartmentalize cAMP signaling transduced by β2-adrenergic receptors (β(2)ARs); such compartmentalization ensures speed and fidelity of cAMP signaling and effects on cell function. This study aimed to assess the role of AKAPs in regulating global and compartmentalized β(2)AR signaling in human airway smooth muscle (ASM). Transcriptome and proteomic analyses were used to characterize AKAP expression in ASM. Stable expression or injection of peptides AKAP-IS or Ht31 was used to disrupt AKAP-PKA interactions, and global and compartmentalized cAMP accumulation stimulated by β-agonist was assessed by radioimmunoassay and membrane-delineated flow through cyclic nucleotide-gated channels, respectively...

BACKGROUND: AKAP12/Gravin (A kinase anchor protein 12) is one of the A-kinase scaffold proteins and a potential tumor suppressor gene in human primary cancers. Our recent study demonstrated the highly recurrent loss of AKAP12 in colorectal cancer and AKAP12 reexpression inhibited proliferation and anchorage-independent growth in colorectal cancer cells, implicating AKAP12 in colorectal cancer pathogenesis. METHODS: To evaluate the effect of this gene on the progression and metastasis of colorectal cancer, we examined the impact of overexpressing AKAP12 in the AKAP12-negative human colorectal cancer cell line LoVo, the single clone (LoVo-AKAP12) compared to mock-transfected cells (LoVo-CON)...

The product of the SSeCKS/GRAVIN/AKAP12 gene ("SSeCKS") is a major protein kinase (PK) C substrate that exhibits tumor- and metastasis-suppressing activity likely through its ability to scaffold multiple signaling mediators such as PKC, PKA, cyclins, calmodulin, and Src. Although SSeCKS and PKCα bind phosphatidylserine, we demonstrate that phosphatidylserine-independent binding of PKC by SSeCKS is facilitated by two homologous SSeCKS motifs, EG(I/V)(T/S)XWXSFK(K/R)(M/L)VTP(K/R)K(K/R)X(K/R)XXXEXXXE(E/D) (amino acids 592-620 and 741-769)...

Emerging data suggest that SSeCKS/Gravin/AKAP12 ("AKAP12"), originally identified as an autoantigen in cases of myasthenia gravis, controls multiple biological processes through its ability to scaffold key signaling proteins such as protein kinase (PK) C and A, calmodulin, cyclins, phosphoinositides, "long" β-1,4 galactosyltransferase (GalTase) isoform, Src, as well as the actin cytoskeleton in a spatiotemporal manner. Specialized functions attributed to AKAP12 include the suppression of cancer malignancy, especially aspects of metastatic progression, regulation of blood-brain and blood-retina barrier formation, and resensitization of β2-adrenergic pain receptors...

BACKGROUND: A-kinase-anchoring proteins, AKAPs, constitute a family of scaffolds that play an essential role in catalyzing the spatial-temporal, dynamic interactions of protein kinase A, protein kinase C, tyrosine kinases, G-protein-coupled receptors and ion channels. We studied AKAP5 (AKAP79; MW ~47 kDa) and AKAP12 (gravin, SSECKS; MW ~191 kDa) to probe if these AKAP scaffolds oligomerize. RESULTS: In gel analysis and sodium-dodecyl sulfate denaturation, AKAP12 behaved with a MW of a homo-dimer...

BACKGROUND: A kinase anchor protein 12 (AKAP12/gravin) belongs to a family of scaffold proteins and organizes protein kinase (PK)A and PKC. DNA hypermethylation in the AKAP12 promoter region has been reported in a variety of human cancers with the exception of skin cancer. Methylation-specific high-resolution melting (MS-HRM) analysis is a novel tool for analysis of promoter methylation. AIM: To use MS-HRM analysis to detect the methylation levels of the AKAP12 gene in skin samples...

The ability of SSeCKS/Gravin/AKAP12 (SSeCKS) to negatively regulate cell cycle progression is thought to relate to its spatiotemporal scaffolding activity for key signaling molecules such as protein kinase A and C, calmodulin and cyclins. SSeCKS is downregulated upon progression to malignancy in many cancer types, including melanoma and nonmelanoma skin cancer. The forced re-expression of SSeCKS is especially potent in suppressing metastasis through the inhibition of VEGF-mediated neovascularization. We have previously shown that SSeCKS-null (KO) mice exhibit hyperplasia and focal dysplasia in the prostate marked by activated Akt...

A subset of AKAPs (A Kinase Anchoring Proteins) regulate signaling and cytoskeletal pathways through the spaciotemporal scaffolding of multiple protein kinases (PK) such as PKC and PKA, and associations with the plasma membrane and the actin-based cytoskeleton. SSeCKS/Gravin/Akap12 expression is severely downregulated in many advanced cancers and exhibits tumor- and metastasis-suppressing activity. akap12-null (KO) mice develop prostatic hyperplasia with focal dysplasia, but the precise mechanism how Akap12 prevents oncogenic progression remains unclear...

The SSeCKS/Gravin/AKAP12 gene, encoding a kinase scaffolding protein with metastasis-suppressing activity, is transcriptionally downregulated in Src-transformed cells through the recruitment of HDAC1 to a Src-responsive proximal promoter site charged with Sp1, Sp3 and USF1. However, the ectopic expression of these proteins formed a suppressive complex in Src-transformed but not in parental NIH3T3 cells, suggesting the involvement of additional repressor factors. Transcription factor II-I (TFII-I) [general transcription factor 2i (Gtf2i)] was identified by mass spectrometry as being associated with the SSeCKS promoter complex in NIH3T3/Src cells, and moreover, the Src-induced tyrosine phosphorylation of TFII-I significantly increased its binding to the SSeCKS proximal promoter...