Dibutyryl cAMP- or Interleukin-6-induced astrocytic differentiation enhances mannose binding lectin (MBL)-associated serine protease (MASP)-1/3 expression in C6 glioma cells.

Mannose-binding lectin (MBL)-Associated Serine Proteases (MASP)-1 and 3, key enzymes in the lectin complement pathway of innate immune response, are also expressed in glioma cell lines. We investigated MASP-1 and MASP-3 expression during dibutyryl cyclic AMP (dbcAMP)- or Interleukin-6 (rIL-6)-induced astrocytic differentiation of C6 glioma cells. Our results demonstrate that C6 cells express basal levels of MASP-1 and MASP-3 and following exposure to dbcAMP or IL-6, a consistent MASP-1 and MASP-3 mRNA up-regulation was found, with a behavior similar to that showed by the fibrillary acidic protein (GFAP). Furthermore, in cell conditioned media, rIL-6 stimulated MASP-3 secretion which reached levels similar to those obtained by dbcAMP treatment. Moreover, the detection of a 46-kDa MASP-3 suggested its processing to the mature form in the extracellular cell medium. Interestingly, the H89 PKA inhibitor, mostly affected dbcAMP-induced MASP-1 and MASP-3 mRNA levels, compared to that of rIL-6, suggesting that cAMP/PKA pathway contributes to MASP-1 and MASP-3 up-regulation. MASP-1 and MASP-3 expression increase was concomitant with dbcAMP- or rIL-6-induced phosphorylation of STAT3. Our findings suggest that the increase in intracellular cAMP concentration or rIL-6 stimulation can play a role in innate immunity enhancing MASP-1 and MASP-3 expression level in C6 glioma cells.

Post-ischemic treatment with azithromycin protects ganglion cells against retinal ischemia/reperfusion injury in the rat.

Purpose: Retinal ischemic phenomena occur in several ocular diseases that share the degeneration and death of retinal ganglion cells (RGCs) as the final event. We tested the neuroprotective effect of azithromycin, a widely used semisynthetic macrolide antibiotic endowed with anti-inflammatory and immunomodulatory properties, in a model of retinal ischemic injury induced by transient elevation of intraocular pressure in the rat. Methods: Retinal ischemia was induced in adult rats with transient elevation of intraocular pressure. RGCs were retrogradely labeled with Fluoro-Gold, and survival was assessed following a single dose of azithromycin given systemically at the end of the ischemia. The expression of death-associated proteins and extracellular signal-regulated kinase (ERK) activation was studied with western blotting. Expression and activity of matrix metalloproteinase-2 (MMP-2) and -9 were analyzed with gelatin zymography. Results: Acute post-injury administration of azithromycin significantly prevented RGC death. This effect was accompanied by reduced calpain activity and prevention of Bcl-2-associated death promoter (Bad) upregulation. The observed neuroprotection was associated with a significant inhibition of MMP-2/-9 gelatinolytic activity and ERK1/2 phosphorylation. Conclusions: Azithromycin provides neuroprotection by modifying the inflammatory state of the retina following ischemia/reperfusion injury suggesting potential for repurposing as a drug capable of limiting or preventing retinal neuronal damage.

Protease Nexin-1 affects the migration and invasion of C6 glioma cells through the regulation of urokinase Plasminogen Activator and Matrix Metalloproteinase-9/2.

Protease Nexin-1 (PN-1) or Serpine2 is a physiological regulator of extracellular proteases as thrombin and urokinase (uPA) in the brain. Besides, PN-1 is also implicated in some human cancers and further identified as a substrate for Matrix Metalloproteinase (MMP)-9, a key enzyme in tumor invasiveness. Our aim was to study the role of PN-1 in the migration and invasive potential of glioma cells, using the rat C6 glioma cell line as stable clones transfected with pAVU6+27 vector expressing PN-1 short-hairpin RNA. We find that PN-1 knockdown enhanced the in vitro migration and invasiveness of C6 cells which also showed a strong gelatinolytic activity by in situ zymography. PN-1 silencing did not alter prothrombin whereas increased uPA, MMP-9 and MMP-2 expression levels and gelatinolytic activity in a conditioned medium from stable C6 cells. Selective inhibitors for MMP-9 (Inhibitor I), MMP-2 (Inhibitor III) or exogenous recombinant PN-1 added to the culture medium of C6 silenced cells restored either the migration and invasive ability or gelatinolytic activity thus validating the specificity of PN-1 silencing strategy. Phosphorylation levels of extracellular signal-related kinases (Erk1/2 and p38 MAPK) involved in MMP-9 and MMP-2 signaling were increased in PN-1 silenced cells. This study shows that PN-1 affects glioma cell migration and invasiveness through the regulation of uPA and MMP-9/2 expression levels which contribute to the degradation of extracellular matrix during tumor invasion.

NCX3 regulates mitochondrial Ca(2+) handling through the AKAP121-anchored signaling complex and prevents hypoxia-induced neuronal death.

The mitochondrial influx and efflux of Ca(2+) play a relevant role in cytosolic and mitochondrial Ca(2+) homeostasis, and contribute to the regulation of mitochondrial functions in neurons. The mitochondrial Na(+)/Ca(2+) exchanger, which was first postulated in 1974, has been primarily investigated only from a functional point of view, and its identity and localization in the mitochondria have been a matter of debate over the past three decades. Recently, a Li(+)-dependent Na(+)/Ca(2+) exchanger extruding Ca(2+) from the matrix has been found in the inner mitochondrial membrane of neuronal cells. However, evidence has been provided that the outer membrane is impermeable to Ca(2+) efflux into the cytoplasm. In this study, we demonstrate for the first time that the nuclear-encoded NCX3 isoform (1) is located on the outer mitochondrial membrane (OMM) of neurons; (2) colocalizes and immunoprecipitates with AKAP121 (also known as AKAP1), a member of the protein kinase A anchoring proteins (AKAPs) present on the outer membrane; (3) extrudes Ca(2+) from mitochondria through AKAP121 interaction in a PKA-mediated manner, both under normoxia and hypoxia; and (4) improves cell survival when it works in the Ca(2+) efflux mode at the level of the OMM. Collectively, these results suggest that, in neurons, NCX3 regulates mitochondrial Ca(2+) handling from the OMM through an AKAP121-anchored signaling complex, thus promoting cell survival during hypoxia.

Intravitreal injection of forskolin, homotaurine, and L-carnosine affords neuroprotection to retinal ganglion cells following retinal ischemic injury.

PURPOSE: Retinal ganglion cell (RGC) death is the final event leading to visual impairment in glaucoma; therefore, identification of neuroprotective strategies able to slow down or prevent the process is one of the main challenges for glaucoma research. The purpose of this study was to evaluate the neuroprotective potential of RGC death induced by the in vivo transient increase in intraocular pressure (IOP) of a combined treatment with forskolin, homotaurine, and L-carnosine. Forskolin (7beta-acetoxy-8, 13-epoxy-1a, 6ß, 9a-trihydroxy-labd-14-en-11-one) is an activator of adenylate cyclase that decreases IOP by reducing aqueous humor production and functions as a neuroprotector due to its neurotrophin-stimulating activity. Homotaurine is a natural aminosulfonate compound endowed with neuromodulatory effects, while the dipeptide L-carnosine is known for its antioxidant properties. METHODS: Retinal ischemia was induced in the right eye of adult male Wistar rats by acutely increasing the IOP. Forskolin, homotaurine, and L-carnosine were intravitreally injected and RGC survival evaluated following retrograde labeling with FluoroGold. Total and phosphorylated Akt and glycogen synthase kinase-3ß (GSK-3ß) protein levels, as well as calpain activity, were analyzed with western blot. Protein kinase A (PKA) was inhibited by intravitreal injection of H89. RESULTS: A synergic neuroprotective effect on RGC survival was observed following the combined treatment with forskolin, homotaurine, and L-carnosine compared to forskolin alone. The observed neuroprotection was associated with reduced calpain activity, upregulation of phosphoinositide 3-kinase (PI3K)/Akt pathway, and inhibition of GSK-3ß but was independent from PKA activation and distinct from the hypotensive effects of forskolin. CONCLUSIONS: A multidrug/multitarget approach, by interfering with several pathways involved in RGC degeneration, may be promising to achieve glaucoma neuroprotection.

Neuroprotective Effect of a Nutritional Supplement Containing Spearmint Extract, Forskolin, Homotaurine and Group B Vitamins in a Mouse Model of Transient Ocular Hypertension.

Glaucoma is one of the most common sight-threatening eye disorders and one of the main causes of irreversible blindness worldwide. The current therapies focusing on reducing intraocular pressure (IOP) are often insufficient to prevent the progression of the disease, so the therapeutic management of glaucoma remains a challenge. The aim of this study was to evaluate the neuroprotective, IOP-lowering independent effects of a nutritional supplement containing forskolin, homotaurine, spearmint extract and vitamins of the B group in a model of acute glaucoma developed in mice. Glaucoma was induced in adult wild-type C57BL/6J mice by transient elevation of IOP. The dietary supplement, branded as Gangliomix® (125 mg/kg/day), was administered by oral gavage for 17 days and ocular hypertension was induced on the 10th day of treatment. A histological analysis of the retinas was performed and RGC survival was evaluated with fluorogold labeling and Brn3a immunostaining on wholemount and retinal sections. Expression of alpha-spectrin, caspase-3, PARP-1 and GFAP was studied with western blotting or immunofluorescence. A significant increase in RGC survival was reported in the retina of mice treated with the dietary supplement as compared to vehicle-treated animals. The observed neuroprotection was associated with a calpain activity decrease, reduction in caspase-3 and PARP-1 activation, and prevention of GFAP upregulation. These effects were independent from the hypotensive effects of the supplement. Altogether, our data suggest that the dietary supplementation with forskolin, homotaurine, spearmint extract and vitamins of the B group supports RGC survival and may offer beneficial effects in glaucoma patients in combination with the currently used IOP-lowering therapy.

Early and late events induced by polyQ-expanded proteins: identification of a common pathogenic property of polYQ-expanded proteins.

To find a common pathogenetic trait induced by polyQ-expanded proteins, we have used a conditional expression system in PC12 cells to tune the expression of these proteins and analyze the early and late consequences of their expression. We find that expression for 3 h of a polyQ-expanded protein stimulates cellular reactive oxygen species (ROS) levels and significantly reduces the mitochondrial electrochemical gradient. 24-36 h later, ROS induce DNA damage and activation of the checkpoint kinase, ATM. DNA damage signatures are reversible and persist as long as polyQ-expanded proteins are expressed. Transcription of neural and stress response genes is down-regulated in these cells. Selective inhibition of ATM or histone deacetylase rescues transcription and restores the expression of silenced genes. Eventually, after 1 week, the expression of polyQ-expanded protein also induces endoplasmic reticulum stress. As to the primary mechanism responsible for ROS generation, we find that polyQ-expanded proteins, including native Ataxin-2 and Huntingtin, are selectively sequestered in the lipid raft membrane compartment and interact with gp91, the membrane NADPH-oxidase subunit. Selective inhibition of NADPH oxidase or silencing of H-Ras signaling dissolves the aggregates and eliminates DNA damage. We suggest that targeting of the polyQ-expanded proteins to the lipid rafts activates the resident NADPH oxidase. This triggers a signal linking H-Ras, ROS, and ERK1/2 that maintains and propagates the ROS wave to the nucleus. This mechanism may represent the common pathogenetic signature of all polyQ-expanded proteins independently of the specific context or the function of the native wild type protein.

Proteolysis of AKAP121 regulates mitochondrial activity during cellular hypoxia and brain ischaemia.

A-kinase anchor protein 121 (AKAP121) assembles a multivalent signalling complex on the outer mitochondrial membrane that controls persistence and amplitude of cAMP and src signalling to mitochondria, and plays an essential role in oxidative metabolism and cell survival. Here, we show that AKAP121 levels are regulated post-translationally by the ubiquitin/proteasome pathway. Seven In-Absentia Homolog 2 (Siah2), an E3-ubiquitin ligase whose expression is induced in hypoxic conditions, formed a complex and degraded AKAP121. In addition, we show that overexpression of Siah2 or oxygen and glucose deprivation (OGD) promotes Siah2-mediated ubiquitination and proteolysis of AKAP121. Upregulation of Siah2, by modulation of the cellular levels of AKAP121, significantly affects mitochondrial activity assessed as mitochondrial membrane potential and oxidative capacity. Also during cerebral ischaemia, AKAP121 is degraded in a Siah2-dependent manner. These findings reveal a novel mechanism of attenuation of cAMP/PKA signaling, which occurs at the distal sites of signal generation mediated by proteolysis of an AKAP scaffold protein. By regulating the stability of AKAP121-signalling complex at mitochondria, cells efficiently and rapidly adapt oxidative metabolism to fluctuations in oxygen availability.

The promise of neuroprotection by dietary restriction in glaucoma.

Glaucoma, a progressive age-related optic neuropathy characterized by the death of retinal ganglion cells, is the most common neurodegenerative cause of irreversible blindness worldwide. The therapeutic management of glaucoma, which is limited to lowering intraocular pressure, is still a challenge since visual loss progresses in a significant percentage of treated patients. Restricted dietary regimens have received considerable attention as adjuvant strategy for attenuating or delaying the progression of neurodegenerative diseases. Here we discuss the literature exploring the effects of modified eating patterns on retinal aging and resistance to stressor stimuli.

Autophagy: A Novel Pharmacological Target in Diabetic Retinopathy.

Autophagy is the major catabolic pathway involved in removing and recycling damaged macromolecules and organelles and several evidences suggest that dysfunctions of this pathway contribute to the onset and progression of central and peripheral neurodegenerative diseases. Diabetic retinopathy (DR) is a serious complication of diabetes mellitus representing the main preventable cause of acquired blindness worldwide. DR has traditionally been considered as a microvascular disease, however this concept has evolved and neurodegeneration and neuroinflammation have emerged as important determinants in the pathogenesis and evolution of the retinal pathology. Here we review the role of autophagy in experimental models of DR and explore the potential of this pathway as a target for alternative therapeutic approaches.

Development and Translation of NanoBEO, a Nanotechnology-Based Delivery System of Bergamot Essential Oil Deprived of Furocumarins, in the Control of Agitation in Severe Dementia.

Dementia is one of the most common causes of disability worldwide characterized by memory loss, cognitive impairment, and behavioral and psychological symptoms (BPSD), including agitation. Treatment of the latter consists of the off-label use of harmful atypical antipsychotics, though a significant reduction is afforded by pain control. The use of an essential oil endowed with analgesic properties and devoid of toxicity would represent an important option for the management of agitation in dementia. Therefore, the aim of this study was to engineer a nanotechnology delivery system based on solid lipid nanoparticles loaded with bergamot essential oil (BEO) and devised in the pharmaceutical form of an odorless cream (NanoBEO) to confirm its analgesic efficacy for further development and application to control agitation in dementia. BEO has proven strong antinociceptive and anti-allodynic properties and, in its bergapten-free form, it is completely devoid of phototoxicity. NanoBEO has been studied in vivo confirming the previously reported analgesic activity of BEO to which is now added its anti-itching properties. Due to the nanotechnology delivery system, the stability of titrated BEO components is guaranteed. Finally, the latter invention, currently under patent consideration, is smell-devoid allowing efficacy and safety to be established in double-blind clinical trials; until now the latter studies have been impeded in aromatherapy by the strong odor of essential oils. A clinical trial NCT04321889 has been designed to provide information about the efficacy and safety of NanoBEO on agitation and pain in patients suffering from severe dementia.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma.

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

The Role of Autophagy in Glaucomatous Optic Neuropathy.

Autophagy is a conserved lysosomal-dependent pathway responsible for the degradation of cytoplasmic macromolecules. Based on the mechanism of cargo delivery to lysosomes, mammalian cells can undergo micro, macro, and chaperone-mediated autophagy. Other than physiological turnover of proteins and organelles, autophagy regulates cellular adaptation to different metabolic states and stressful conditions by allowing cellular survival or, when overactivated, participating to cell death. Due to their structure and function, neurons are highly dependent on autophagy efficiency and dysfunction of the pathway has been associated with neurodegenerative disorders. Glaucomatous optic neuropathies, a leading cause of blindness, are characterized by the progressive loss of a selective population of retinal neurons, i.e., the retinal ganglion cells (RGCs). Here we review the current literature on the role of autophagy in the pathogenic process that leads to the degeneration of RGC in various experimental models of glaucoma exploring the modulation of the pathway as a potential therapeutic intervention.

Effects of caloric restriction on retinal aging and neurodegeneration.

Glaucoma is the most common neurodegenerative cause of irreversible blindness worldwide. Restricted caloric regimens are an attractive approach for delaying the progression of neurodegenerative diseases. Here we review the current literature on the effects of caloric restriction on retinal neurons, under physiological and pathological conditions. We focused on autophagy as one of the mechanisms modulated by restricted caloric regimens and involved in the death of retinal ganglion cells (RGCs) over the course of glaucoma.

Pattern of triptans use: a retrospective prescription study in Calabria, Italy.

Triptans are 5-hydroxytryptamine 1B/1D receptor agonists used in moderate to severe migraine attacks as first line when non-specific, symptomatic, nonsteroidal anti-inflammatory drugs are not effective. To gain insight in the treatment of migraine in the regional context, this retrospective (from January to August of the years 2017 and 2018) study aimed at monitoring the use of triptans approved by the regional health authority in Calabria. The data demonstrate that the overall treatment of migraine with triptans in the different provinces of Calabria falls in the average regional prescription/dispensation. Interestingly, Crotone showed a trend to an increased amount of defined daily dose/1000 inhabitants per day. The present analysis might stand for homogeneity of treatment of migraineurs in Calabria and highlights the need for better understanding the apparent differences in the local pattern of almotriptan use to improve the appropriateness.

Targeted disruption of Na+/Ca2+ exchanger 3 (NCX3) gene leads to a worsening of ischemic brain damage.

Na+/Ca+ exchanger 3 (NCX3), one of the three isoforms of the NCX family, is highly expressed in the brain and is involved in the maintenance of intracellular Na+ and Ca2+ homeostasis. Interestingly, whereas the function of NCX3 under physiological conditions has been determined, its role under anoxia is still unknown. To assess NCX3 role in cerebral ischemia, we exposed ncx3-/- mice to transient middle cerebral artery occlusion followed by reperfusion. In addition, to evaluate the effect of ncx3 ablation on neuronal survival, organotypic hippocampal cultures and primary cortical neurons from ncx3-/- mice were subjected to oxygen glucose deprivation (OGD) plus reoxygenation. Here we report that ncx3 gene suppression leads to a worsening of brain damage after focal ischemia and to a massive neuronal death in all the hippocampal fields of organotypic cultures as well as in cortical neurons from ncx3-/- mice exposed to OGD plus reoxygenation. In addition, in ncx3-/- cortical neurons exposed to hypoxia, NCX currents, recorded in the reverse mode of operation, were significantly lower than those detected in ncx3+/+. From these results, NCX3 protein emerges as a new molecular target that may have a potential therapeutic value in modulating cerebral ischemia.

A critical role for the potassium-dependent sodium-calcium exchanger NCKX2 in protection against focal ischemic brain damage.

The superfamily of cation/Ca2+ plasma-membrane exchangers contains two branches, the K+-independent Na+-Ca2+ exchangers (NCXs) and the K+-dependent Na+-Ca2+ exchangers (NCKXs), widely expressed in mammals. NCKX2 is the major neuronally expressed isoform among NCKX members. Despite its importance in maintaining Na+, Ca2+, and K+ homeostasis in the CNS, the role of NCKX2 during cerebral ischemia, a condition characterized by an alteration of ionic concentrations, has not yet been investigated. The present study examines NCKX2 role in the development of ischemic brain damage in permanent middle cerebral artery occlusion (pMCAO) and transient middle cerebral artery occlusion. Furthermore, to evaluate the effect of nckx2 ablation on neuronal survival, nckx2-/- primary cortical neurons were subjected to oxygen glucose deprivation plus reoxygenation. NCKX2 mRNA and protein expression was evaluated in the ischemic core and surrounding ipsilesional areas, at different time points after pMCAO in rats. In ischemic core and in periinfarctual area, NCKX2 mRNA and protein expression were downregulated. In addition, NCKX2 knock-down by antisense oligodeoxynucleotide and NCKX2 knock-out by genetic disruption dramatically increased infarct volume. Accordingly, nckx2-/- primary cortical neurons displayed a higher vulnerability and a greater [Ca2+]i increase under hypoxic conditions, compared with nckx2+/+ neurons. In addition, NCKX currents both in the forward and reverse mode of operation were significantly reduced in nckx2-/- neurons compared with nckx2+/+ cells. Overall, these results indicate that NCKX2 is involved in brain ischemia, and it may represent a new potential target to be investigated in the study of the molecular mechanisms involved in cerebral ischemia.

Anoxia-induced NF-kappaB-dependent upregulation of NCX1 contributes to Ca2+ refilling into endoplasmic reticulum in cortical neurons.

BACKGROUND AND PURPOSE: The 3 gene products of the Na(+)/Ca(2+) exchanger (NCX), viz, NCX1, NCX2, and NCX3, may play a pivotal role in the pathophysiology of brain ischemia. The aim of this study was to investigate the transductional and posttranslational mechanisms involved in the expression of these isoforms during oxygen and glucose deprivation and their role in endoplasmic reticulum Ca(2+) refilling in cortical neurons. METHODS: NCX1, NCX2, and NCX3 transcript and protein expression was evaluated in primary cortical neurons by reverse transcriptase-polymerase chain reaction and Western blot. NCX currents (I(NCX)) and cytosolic Ca(2+) concentrations ([Ca(2+)](i)) were monitored by means of patch-clamp in whole-cell configuration and Fura-2AM single-cell video imaging, respectively. RESULTS: Exposure of cortical neurons to 3 hours of oxygen and glucose deprivation yielded dissimilar effects on the 3 isoforms. First, it induced an upregulation in NCX1 transcript and protein expression. This change was exerted at the transcriptional level because the inhibition of nuclear factor kappa B translocation by small interfering RNA against p65 and SN-50 prevented oxygen and glucose deprivation-induced NCX1 upregulation. Second, it elicited a downregulation of NCX3 protein expression. This change, unlike NCX1, was exerted at the posttranscriptional level because it was prevented by the proteasome inhibitor MG-132. Finally, we found that it significantly increased I(NCX) both in the forward and reverse modes of operation and promoted an increase in ER Ca(2+) accumulation. Interestingly, such accumulation was prevented by the silencing of NCX1 and the NCX inhibitor CB-DMB that triggered caspase-12 activation. CONCLUSIONS: These results suggest that nuclear factor kappa B-dependent NCX1 upregulation may play a fundamental role in Ca(2+) refilling in the endoplasmic reticulum, thus helping neurons to prevent endoplasmic reticulum stress during oxygen and glucose deprivation.

Mitochondrial AKAP121 links cAMP and src signaling to oxidative metabolism.

AKAP121 focuses distinct signaling events from membrane to mitochondria by binding and targeting cAMP-dependent protein kinase (PKA), protein tyrosine phosphatase (PTPD1), and mRNA. We find that AKAP121 also targets src tyrosine kinase to mitochondria via PTPD1. AKAP121 increased src-dependent phosphorylation of mitochondrial substrates and enhanced the activity of cytochrome c oxidase, a component of the mitochondrial respiratory chain. Mitochondrial membrane potential and ATP oxidative synthesis were enhanced by AKAP121 in an src- and PKA-dependent manner. Finally, siRNA-mediated silencing of endogenous AKAP121 drastically impaired synthesis and accumulation of mitochondrial ATP. These findings indicate that AKAP121, through its role in enhancing cAMP and tyrosine kinase signaling to distal organelles, is an important regulator in mitochondrial metabolism.