Identification and Characterization of Myeloid Translocation Gene 16b as a Novel A Kinase Anchoring Protein in T Lymphocytes

Abstract

Increased levels of intracellular cAMP inhibit T cell activation and proliferation. One mechanism is via activation of the cAMP-dependent protein kinase (PKA). PKA is a broad specificity serine/threonine kinase whose fidelity in signaling is maintained through interactions with A kinase anchoring proteins (AKAPs). AKAPs are adaptor/scaffolding molecules that convey spatial and temporal localization to PKA and other signaling molecules. To determine whether T lymphocytes contain AKAPs that could influence the inflammatory response, PBMCs and Jurkat cells were analyzed for the presence of AKAPs. RII overlay and cAMP pull down assays detected at least six AKAPs. Western blot analyses identified four known AKAPs: AKAP79, AKAP95, AKAP149, and WAVE. Screening of a PMA-stimulated Jurkat cell library identified two additional known AKAPs, AKAP220 and AKAP-KL, and one novel AKAP, myeloid translocation gene 16 (MTG16b). Mutational analysis identified the RII binding domain in MTG16b as residues 399–420, and coimmunoprecipitation assays provide strong evidence that MTG16b is an AKAP in vivo. Immunofluorescence and confocal microscopy illustrate distinct subcellular locations of AKAP79, AKAP95, and AKAP149 and suggest colocalization of MTG and RII in the Golgi. These experiments represent the first report of AKAPs in T cells and suggest that MTG16b is a novel AKAP that targets PKA to the Golgi of T lymphocytes.

Protein kinase A-anchoring (AKAP) domains in brefeldin A-inhibited guanine nucleotide-exchange protein 2 (BIG2)

“…A recent report of overexpression of RII␣ in an RII␣-deficient B lymphoid cell line (Reh) indicated a regulatory role for Golgi-associated PKA in transport of ricin, a plant toxin, from endosomes to Golgi (31). Two other Golgi-localized AKAPs, myeloid translocation gene 16b (32) and AKAP350 (33), have also been described.…”

A‐kinase anchoring protein 3 messenger RNA expression in ovarian cancer and its implication on prognosis

“…8,20,21 It has been shown that AKAP75 overexpression inhibited smooth muscle cell proliferation in vitro and in vivo by inducing cyclin-dependent kinase-2 inhibitor p27 kip1 . 9,22 Moreover, an increased level of intracellular cAMP inhibited T cell proliferation 10,11 and induced apoptosis in cancer cells. 13,[23][24][25][26][27] The effect on the proliferation of ovarian cancer cells of the agents such as taxanes in augmenting AKAP3 mRNA expression should be investigated.…”

“…8 Recently, it has been demonstrated that AKAP-mediated PKA activation inhibited cell growth in the muscle 9 and T lymphocytes. 10,11 Paclitaxel, docetaxel and vincristine, which were shown to damage microtubules, also activate PKA and induce hyperphosphorylation of Bcl-2, cause growth arrest and apoptosis. 12,13 Chemotherapy using a paclitaxel-based regimen is now commonly used for the treatment of postoperative ovarian cancer patients.…”

Regulating small G protein signaling to coordinate axon adhesion and repulsion

“…Small GTPases have GTP hydrolysis activity, thereby working as molecular switches that are functional in the GTP bound form and turned-off in the GDP bound form. GTP bound GTPases preferentially associate with downstream effectors such as Rho kinase (ROCK), p21-activated kinase (PAK), phosphatidylinositol-4-phosphate interact with Nervy/MTG family proteins, which among other roles have been found to function as protein kinase A (A kinase) anchoring proteins (AKAPs) 25,26 and link protein kinase A (PKA) to the Plexin A receptor (Fig. 1A).…”