NUDC is critical for rod photoreceptor function, maintenance, and survival

NUDC (nuclear distribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (rNudC-/- ). Loss of NUDC in rods led to complete photoreceptor cell death at 6 weeks of age. By 3 weeks of age, rNudC-/- function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of rNudC-/- by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. The absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.

NUDC is critical for rod photoreceptor function, maintenance, and survival

NUDC ( nu clear d istribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (r NudC -/- ). Loss of NUDC in rods led to complete photoreceptor cell death at six weeks of age. By 3 weeks of age, r NudC -/- function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of r NudC -/- by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. Absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.

Significance Statement

Nuclear distribution protein C (NUDC) has been studied extensively as an essential protein for mitotic cell division. In this study, we discovered its expression and role in the postmitotic rod photoreceptor cell. In the absence of NUDC in mouse rods, we detected functional loss, protein mislocalization, and rapid retinal degeneration consistent with dynein inactivation. In the early phase of retinal degeneration, we observed ultrastructural defects and an upregulation of inflammatory markers suggesting additional, dynein-independent functions of NUDC.

Retinal electrophysiologic response to IOP elevation in living human eyes

PURPOSE

The relationships between intraocular pressure (IOP), ocular perfusion pressure (OPP), retinal perfusion, and retinal electrophysiologic responses have been explored experimentally across several animal models. These studies have demonstrated that elevated IOP reduces OPP, and when this reduction in OPP exceeds the autoregulatory capacity of the retina vasculature, retinal perfusion and electrophysiologic responses are reduced. This study aimed to evaluate these interactions for the first time in the living human eye.

METHODS

Five eyes from three research-consented brain-dead organ donors underwent optical coherence tomography with angiographic (OCT/A; Spectralis, Heidelberg Engineering) and electroretinographic (ERG, Diagnosys LLC) measurements while IOP was manometrically-elevated stepwise to pressures of 10, 30 and 50 mmHg. Systemic blood pressure (BP) was monitored continuously during testing. Correlation analysis was applied to assess association between ERG and OPP changes. In a single eye, prolonged IOP elevation was induced with viscoelastic injection and serial ERG measurements were obtained.

RESULTS

Reductions in inner retinal function defined by photopic ERG were observed with elevation in IOP and concomitant reduction in OPP. Reductions, especially in b-wave, and photopic negative response (PhNR) amplitudes and implicit times were significantly correlated with elevation in IOP and reduction in OPP. There were more appreciable changes in perfusion and functional responses in eyes tested while systemic blood pressure was lower. With prolonged IOP elevation, selective loss of the PhNR response was observed.

CONCLUSIONS

In the living human eye, retinal perfusion and inner retinal function are acutely impacted by elevation of IOP, and this impact is related to systemic BP and OPP. This novel approach provides a viable model to study the autoregulatory responses to IOP elevation in the living human eye.

Remodeling of the Lamina Cribrosa: Mechanisms and Potential Therapeutic Approaches for Glaucoma

Glaucomatous optic neuropathy is the leading cause of irreversible blindness in the world. The chronic disease is characterized by optic nerve degeneration and vision field loss. The reduction of intraocular pressure remains the only proven glaucoma treatment, but it does not prevent further neurodegeneration. There are three major classes of cells in the human optic nerve head (ONH): lamina cribrosa (LC) cells, glial cells, and scleral fibroblasts. These cells provide support for the LC which is essential to maintain healthy retinal ganglion cell (RGC) axons. All these cells demonstrate responses to glaucomatous conditions through extracellular matrix remodeling. Therefore, investigations into alternative therapies that alter the characteristic remodeling response of the ONH to enhance the survival of RGC axons are prevalent. Understanding major remodeling pathways in the ONH may be key to developing targeted therapies that reduce deleterious remodeling.

Two distinct signaling pathways regulate peroxynitrite-induced apoptosis in PC12 cells

The mechanisms of peroxynitrite-induced apoptosis are not fully understood. We report here that peroxynitrite-induced apoptosis of PC12 cells requires the simultaneous activation of p38 and JNK MAP kinase, which in turn activates the intrinsic apoptotic pathway, as evidenced by Bax translocation to the mitochondria, cytochrome c release to the cytoplasm and activation of caspases, leading to cell death. Peroxynitrite induces inactivation of the Akt pathway. Furthermore, overexpression of constitutively active Akt inhibits both peroxynitrite-induced Bax translocation and cell death. Peroxynitrite-induced death was prevented by overexpression of Bcl-2 and by cyclosporin A, implicating the involvement of the intrinsic apoptotic pathway. Selective inhibition of mixed lineage kinase (MLK), p38 or JNK does not attenuate the decrease in Akt phosphorylation showing that inactivation of the Akt pathway occurs independently of the MLK/MAPK pathway. Together, these results reveal that peroxynitrite-induced activation of the intrinsic apoptotic pathway involves interactions with the MLK/MAPK and Akt signaling pathways.

In vitro aldose reductase inhibitory activity of substituted N-benzenesulfonylglycine derivatives

A number of N-benzenesulfonylglycines, alanines, sarcosine, and prolines, which contain the minimum pharmacophore moieties necessary for aldose reductase inhibitory activity, were prepared and tested in the rat lens assay. In this assay, the benzenesulfonylglycines are considerably more potent than the corresponding alanine and sarcosine derivatives which, in turn, are more active than the proline analogues. Of the monosubstituted benzenesulfonylglycines, the 2-nitro and 4-amino derivatives were most active with 50% inhibitory concentration (IC50) values of 13 and 16 microM, respectively. The most potent derivatives evaluated were the beta- and alpha-naphthylenesulfonylglycines with IC50 values of 0.4 and 1.3 microM, respectively. The structure-activity data obtained from evaluation of the benzenesulfonylamino acids suggests that the aromatic ring and ring substituents, as well as the sulfonamide group and carboxylate moiety, all contribute to the inhibitory potency through direct interaction with complimentary binding sites present on aldose reductase.