Recoverin as a cancer-retina antigen

Case report: A case of anti-recoverin antibody-positive encephalitis exhibiting Cotard and Capgras delusions that was successfully treated with electroconvulsive therapy

Recoverin is a neuron-specific calcium-binding protein that is mainly located in the retina and pineal gland. Few reports have described patients with anti-recoverin antibody-positive encephalitis, and no cases of psychosis associated with this encephalitis have been reported. We report a patient with anti-recoverin antibody-positive encephalitis with Cotard and Capgras delusions who was successfully treated with electroconvulsive therapy (ECT). The patient was a 25-year-old woman. She exhibited disorientation, executive function deficits, tremors in the upper limbs, generalized athetoid-like involuntary movements, hallucinations, incontinence, and fever, which led to her admission to our hospital. Upon admission, she complained of Cotard delusions. Various diagnostic tests, including cerebrospinal fluid analysis, antibody screening, and brain imaging, were unremarkable, except for positivity for serum anti-recoverin antibodies, non-specific general slowing on electroencephalography and decreased regional cerebral blood flow (rCBF) in the frontal and occipital lobes, and increased rCBF in the basal ganglia and pons on single-photon emission computed tomography. She was eventually diagnosed with encephalitis positive for anti-recoverin antibodies and treated with immunoglobulins and steroids. Her neurological symptoms improved temporarily, but three months later, psychiatric symptoms, i.e., suicidal thoughts and Cotard and Capgras delusions, were exaggerated. After ECT, her condition significantly improved. In conclusion, the present report suggests that pineal gland dysfunction due to anti-recoverin antibody or its cross-reactivity with neuron-specific calcium-binding proteins may contribute to the neuropsychiatric symptoms observed in anti-recoverin antibody-positive encephalitis and that ECT can be a viable treatment option if immunotherapy proves ineffective. Additionally, decreased rCBF in the prefrontal cortex may be associated with the clinical features of Capgras and Cotard delusions.

Plasma Antiretinal Autoantibody Profiling and Diagnostic Efficacy in Patients With Autoimmune Retinopathy

PURPOSE

To evaluate plasma antiretinal autoantibody (ARA) profiling and diagnostic efficacy for autoimmune retinopathy (AIR).

DESIGN

A multicenter, diagnostic evaluation study.

METHODS

Forty-nine patients with a clinical diagnosis of AIR, disease controls including 20 patients with retinitis pigmentosa (RP), and 30 normal controls were included. Plasma samples from patients were analyzed for the presence of 6 ARAs, including recoverin, α-enolase, carbonic anhydrase II, heat shock protein 60, aldolase C, and cone-rod homeobox/cone-rod retinal dystrophy 2 using western blotting.

RESULTS

Autoantibody detection rates against cone-rod homeobox/cone-rod retinal dystrophy 2, heat shock protein 60, and aldolase C in AIR were 67.3%, 40.8%, and 42.9%, respectively, which were higher than those in RP and normal controls (P < .001, P < .001, and P = .007, respectively), but recoverin, α-enolase, and carbonic anhydrase II were not different from other control groups (P = .117, P = .774, and P = .467, respectively). Among ARAs, antirecoverin antibody was the most specific, as it was found in 3 (6.1%) patients with AIR and none of the control groups. As the number of detected ARAs increased, the probability of AIR increased (odds ratio: 1.913; P < .001; 95% confidence interval: 1.456-2.785). The positive number of ARAs was significantly higher when photoreceptor disruption was observed on optical coherence tomography, or severe dysfunction was observed in electroretinography (P = .022 and P = .029, respectively).

CONCLUSIONS

The profiles of ARAs in the AIR group were different from those in the RP and normal controls. The higher number of positive ARAs suggests a higher possibility of AIR diagnosis. ARAs should be used as adjunct tools for the clinical diagnosis of AIR.

Timed Notch Inhibition Drives Photoreceptor Fate Specification in Human Retinal Organoids

Purpose

Transplanting photoreceptors from human pluripotent stem cell-derived retinal organoids have the potential to reverse vision loss in affected individuals. However, transplantable photoreceptors are only a subset of all cells in the organoids. Hence, the goal of our current study was to accelerate and synchronize photoreceptor differentiation in retinal organoids by inhibiting the Notch signaling pathway at different developmental time-points using a small molecule, PF-03084014 (PF).

Methods

Human induced pluripotent stem cell- and human embryonic stem cells-derived retinal organoids were treated with 10 µM PF for 3 days starting at day 45 (D45), D60, D90, and D120 of differentiation. Organoids were collected at post-treatment days 14, 28, and 42 and analyzed for progenitor and photoreceptor markers and Notch pathway inhibition by immunohistochemistry (IHC), quantitative PCR, and bulk RNA sequencing (n = 3-5 organoids from three independent experiments).

Results

Retinal organoids collected after treatment showed a decrease in progenitor markers (KI67, VSX2, PAX6, and LHX2) and an increase in differentiated pan-photoreceptor markers (OTX2, CRX, and RCVRN) at all organoid stages except D120. PF-treated organoids at D45 and D60 exhibited an increase in cone photoreceptor markers (RXRG and ARR3). PF treatment at D90 revealed an increase in cone and rod photoreceptors markers (ARR3, NRL, and NR2E3). Bulk RNA sequencing analysis mirrored the immunohistochemistry data and quantitative PCR confirmed Notch effector inhibition.

Conclusions

Timing the Notch pathway inhibition in human retinal organoids to align with progenitor competency stages can yield an enriched population of early cone or rod photoreceptors.

A Novel Approach to Bacterial Expression and Purification of Myristoylated Forms of Neuronal Calcium Sensor Proteins

N-terminal myristoylation is a common co-and post-translational modification of numerous eukaryotic and viral proteins, which affects their interaction with lipids and partner proteins, thereby modulating various cellular processes. Among those are neuronal calcium sensor (NCS) proteins, mediating transduction of calcium signals in a wide range of regulatory cascades, including reception, neurotransmission, neuronal growth and survival. The details of NCSs functioning are of special interest due to their involvement in the progression of ophthalmological and neurodegenerative diseases and their role in cancer. The well-established procedures for preparation of native-like myristoylated forms of recombinant NCSs via their bacterial co-expression with N-myristoyl transferase from Saccharomyces cerevisiae often yield a mixture of the myristoylated and non-myristoylated forms. Here, we report a novel approach to preparation of several NCSs, including recoverin, GCAP1, GCAP2, neurocalcin δ and NCS-1, ensuring their nearly complete N-myristoylation. The optimized bacterial expression and myristoylation of the NCSs is followed by a set of procedures for separation of their myristoylated and non-myristoylated forms using a combination of hydrophobic interaction chromatography steps. We demonstrate that the refolded and further purified myristoylated NCS-1 maintains its Са²⁺-binding ability and stability of tertiary structure. The developed approach is generally suited for preparation of other myristoylated proteins.

Advances in the Development of Anticancer HSP-based Vaccines

Current advances in cancer treatment are based on the recent discoveries of molecular mechanisms of tumour maintenance. It was shown that heat shock proteins (HSPs) play a crucial role in the development of immune response against tumours. Thus, HSPs represent multifunctional agents not only with chaperone functions, but also possessing immunomodulatory properties. These properties are exploited for the development of HSP-based anticancer vaccines aimed to induce cytotoxic responses against tumours. To date, a number of strategies have been suggested to facilitate HSP-based vaccine production and to increase its effectiveness. The present review focuses on the current trend for the development of HSPbased vaccines aimed at inducing strong immunological tumour-specific responses against cancer cells of distinct etiology and localization.

Multiplex bead-based measurement of humoral immune responses against tumor-associated antigens in stage II melanoma patients of the EORTC18961 trial

Purpose: Determine the prognostic and predictive significance of tumor associated antigen (TAA)-specific serum antibodies in melanoma patients of a large adjuvant vaccination phase III trial. Patients and methods: Serum IgG antibodies were measured against a panel of 43 antigens by a bead-based multiplex assay in 970 stage II melanoma patients of the EORTC18961 trial, evaluating adjuvant ganglioside GM2-KLH/QS-21 vaccination versus observation. Primary end point was relapse-free survival (RFS). Patients' sera at baseline, after 12 and 48 weeks of study treatment and at the last available time point (at recurrence/remission) were evaluated. Results: Prognostic clinical variables are gender, surgical confirmation of lymph node-negative status, Breslow thickness and ulceration of the primary. Prognostic spontaneous antibody responses were associated with a significant dismal (GM2, Rhod_E2, SSX2) or good prognosis (CyclinB1, SCYE1v1) for RFS, distant metastasis-free (DMFS) or overall survival (OS). Predictive spontaneous antibody responses based on significant interaction with treatment were RhodN p = 0.02, Rab38 p = 0.04 for RFS, RhodE2 p = 0.006, Recoverin p = 0.04 for DMFS and RhodE2 p = 0.003; Recoverin p = 0.04, NA17.A p = 0.04, for OS respectively. The subgroups of patients according to antibody responses for RFS were determined for RhodN sero-negative (n = 849, HR = 1.07, p = 0.6); RhodN sero-positive (n = 121,HR = 0.42, p = 0.01) and Rab38 sero-negative (n = 682, HR = 1.12, p = 0.42), Rab38 sero-positive (n = 288, HR = 0.65, p = 0.04) patients respectively. Conclusion: We identified prognostic serum antibody responses against TAA in stage II melanoma patients. A set of antibody responses correlated with a beneficial outcome for GM2 vaccination.

The cancer-retina antigen recoverin as a potential biomarker for renal tumors

The renal cell carcinoma is the ninth most common cancer with an increasing occurrence and mortality. Recoverin is the first retina-specific photoreceptor protein that was shown to undergo aberrant expression, due to its promoter demethylation, as a cancer-retina antigen in a number of malignant tumors. In this work, we demonstrated that recoverin is indeed expressed in 68.4 % of patients with different subtypes of renal cell carcinoma, and this expression has tendency to correlate with tumor size. Interestingly, 91.7 % of patients with the benign renal tumor, oncocytoma, express recoverin as well in their tumor. Epigenetic analysis of the recoverin gene promoter revealed a stable mosaic methylation pattern with the predominance of the methylated state, with the exception of -80 and 56 CpG dinucleotides (CpGs). While the recoverin expression does not correlate withoverall survival of the tumor patients, the methylation of the recoverin gene promoter at -80 position is associated with better overall survival of the patients. This work is the first report pointing towards the association of overall survival of renal cell carcinoma (RCC) patients with promoter methylation of a cancer-retina antigen. Taken together, these data allow to consider recoverin as a potential therapeutic target and/or marker for renal tumors.

Cancer-retina antigens -- a new group of tumor antigens

Some photoreceptor proteins normally specific for the eye retina are aberrantly expressed in malignant tumors. These proteins include recoverin, visual rhodopsin, transducin, cGMP-phosphodiesterase 6 (PDE 6), cGMP-dependent cationic channels, guanylyl cyclase 1, rhodopsin kinase, and arrestin. By analogy with cancer-testis antigens, these photoreceptor proteins form the group of cancer-retina antigens. It is shown that an aberrant demethylation of the promoter region of recoverin is involved in the aberrant expression of this protein. The cascade Wnt5a → Frizzled-2 → transducin → PDE 6 is shown to function in skin melanoma cells, and this suggests that these cancer-retina antigens can play a functional role. The events accompanying the signal transduction in this cascade, including those involving calcium ions and cGMP-dependent protein kinase (protein kinase G), are discussed.

Latest updates on antiretinal autoantibodies associated with vision loss and breast cancer

Cancer-associated retinopathy (CAR) is an uncommon paraneoplastic disorder of the retina that is frequently associated with breast cancer in pre- and postmenopausal women older than 50 years. In this review, we will give an update on the current knowledge regarding the association of antiretinal autoantibodies with the breast-CAR syndrome. Women with breast cancer and visual indications of CAR have a significantly increased incidence of autoantibodies (AAbs) against retinal proteins when compared to healthy women. The onset of visual loss in association with antiretinal AAbs peaks 2 to 3 years after the clinical diagnosis of breast cancer. Differences in severity of symptoms between women with or without antiretinal AAbs are evident, revealing more unfavorable presentation in seropositive women. The incidence of CAR in breast cancer is likely to rise as the survival time of patients with breast cancer increases; consequently, a prediction of breast-CAR based on autoimmunity to individual retinal antigens, or to panels of antigens (signatures), is clinically important.

CETN1 is a cancer testis antigen with expression in prostate and pancreatic cancers

BACKGROUND

The Cancer Testis Antigens (CTAs) are a group of genes that are highly expressed in the normal testis and several types of cancer. Due to their restricted expression in normal adult tissues, CTAs have been attractive targets for immunotherapy and biomarker development. In this work, we discovered that Centrin 1 (CETN1) which is found in the centrosome of all eukaryotes, may be a member of this group and is highly expressed in prostate and pancreatic cancer. Three members of the centrin family of calcium binding proteins (CETN) are localized to the centrosome in all eukaryotes with CDC31 being the sole yeast homolog. CETN1 is a retrogene that probably arose from a retrotransposition of CETN2, an X-linked gene. A previous mouse study shows that CETN1 is expressed solely in the testis, while CETN2 is expressed in all organs.

RESULTS

In this work, we show that CETN1 is a new member of the growing group of CTAs. Through the mining of publicly available microarray data, we discovered that human CETN1 expression but not CETN2 or CETN3 is restricted to the testis. In fact, CETN1 is actually down-regulated in testicular malignancies compared to normal testis. Using q-PCR, CETN1 expression is shown to be highly up-regulated in cancer of the prostate and in pancreatic xenografts. Unexpectedly however, CETN1 expression was virtually absent in various cell lines until they were treated with the DNA demethylation agent 5'AZA-2'Deoxycytidine (AZA) but showed no increased expression upon incubation with Histone deacetylase inhibitor Trichostatin-A (TSA) alone. Additionally, like most CTAs, CETN1 appears to be an intrinsically disordered protein which implies that it may occupy a hub position in key protein interaction networks in cancer. Neither CETN1 nor CETN2 could compensate for loss of CDC31 expression in yeast which is analogous to published data for CETN3.

CONCLUSIONS

This work suggests that CETN1 is a novel CTA with expression in cancer of the prostate and pancreas. In cell lines, the expression is probably regulated by promoter methylation, while the method of regulation in normal adult tissues remains unknown.

Good news-bad news: the Yin and Yang of immune privilege in the eye

The eye and the brain are prototypical tissues manifesting immune privilege (IP) in which immune responses to foreign antigens, particularly alloantigens are suppressed, and even completely inhibited. Explanations for this phenomenon are numerous and mostly reflect our evolving understanding of the molecular and cellular processes underpinning immunological responses generally. IP is now viewed as a property of many tissues and the level of expression of IP varies not only with the tissue but with the nature of the foreign antigen and changes in the limited conditions under which privilege can operate as a mechanism of immunological tolerance. As a result, IP functions normally as a homeostatic mechanism preserving normal function in tissues, particularly those with highly specialized function and limited capacity for renewal such as the eye and brain. However, IP is relatively easily bypassed in the face of a sufficiently strong immunological response, and the privileged tissues may be at greater risk of collateral damage because its natural defenses are more easily breached than in a fully immunocompetent tissue which rapidly rejects foreign antigen and restores integrity. This two-edged sword cuts its swathe through the eye: under most circumstances, IP mechanisms such as blood-ocular barriers, intraocular immune modulators, induction of T regulatory cells, lack of lymphatics, and other properties maintain tissue integrity; however, when these are breached, various degrees of tissue damage occur from severe tissue destruction in retinal viral infections and other forms of uveoretinal inflammation, to less severe inflammatory responses in conditions such as macular degeneration. Conversely, ocular IP and tumor-related IP can combine to permit extensive tumor growth and increased risk of metastasis thus threatening the survival of the host.

Comprehensive review on the HSC70 functions, interactions with related molecules and involvement in clinical diseases and therapeutic potential

Heat shock cognate protein 70 (HSC70) is a constitutively expressed molecular chaperone which belongs to the heat shock protein 70 (HSP70) family. HSC70 shares some of the structural and functional similarity with HSP70. HSC70 also has different properties compared with HSP70 and other heat shock family members. HSC70 performs its full functions by the cooperation of co-chaperones. It interacts with many other molecules as well and regulates various cellular functions. It is also involved in various diseases and may become a biomarker for diagnosis and potential therapeutic targets for design, discovery, and development of novel drugs to treat various diseases. In this article, we provide a comprehensive review on HSC70 from the literatures including the basic general information such as classification, structure and cellular location, genetics and function, as well as its protein association and interaction with other proteins. In addition, we also discussed the relationship of HSC70 and related clinical diseases such as cancer, cardiovascular, neurological, hepatic and many other diseases and possible therapeutic potential and highlight the progress and prospects of research in this field. Understanding the functions of HSC70 and its interaction with other molecules will help us to reveal other novel properties of this protein. Scientists may be able to utilize this protein as a biomarker and therapeutic target to make significant advancement in scientific research and clinical setting in the future.

Drop-out phagemid vector for switching from phage displayed affinity reagents to expression formats

Affinity reagents that are generated by phage display are typically subcloned into an expression vector for further biochemical characterization. This insert transfer process is time consuming and laborious especially if many inserts are to be subcloned. To simplify the transfer process, we have constructed a "drop-out" phagemid vector that can be rapidly converted to an expression vector by a simple restriction enzyme digestion with MfeI (to "drop-out" the gene III coding sequence), which generates alkaline phosphatase (AP) fusions of the affinity reagents on religation. Subsequently, restriction digestion with AscI drops out the AP coding region and religation generates affinity reagents with a C-terminal six-histidine tag. To validate the usefulness of this vector, four different human single chain Fragments of variable regions (scFv) were tested, three of which show specific binding to three zebrafish (Danio rerio) proteins, namely suppression of tumorigenicity 13, recoverin, and Ppib and the fourth binds to human Lactoferrin protein. For each of the constructs tested, the gene III and AP drop-out efficiency was between 90% and 100%. This vector is especially useful in speeding up the downstream screening of affinity reagents and bypassing the time-consuming subcloning experiments.

Aberrant demethylation of the recoverin gene is involved in the aberrant expression of recoverin in cancer cells

The Ca(2+) -binding protein recoverin is normally specific for the retina. Recoverin aberrantly expressed in lung and melanoma tumors can trigger the host immune response followed by the development of a paraneoplastic neurological syndrome represented by cancer- and melanoma-associated retinopathy, respectively. The mechanisms, underlying the aberrant expression of recoverin in tumor cells, have remained unknown. The data obtained in this study suggest that (i) DNA methylation participates in the repression of synthesis of mRNA for recoverin in normal tissues and (ii) aberrant hypomethylation of the recoverin gene region, overlapping the promoter up-stream of the first exon and the first exon itself, is involved in the aberrant expression of recoverin in tumor cells.

cGMP-phosphodiesterase 6, transducin and Wnt5a/Frizzled-2-signaling control cGMP and Ca(2+) homeostasis in melanoma cells

Malignant melanoma is one of the most aggressive human neoplasms which develop from the malignant transformation of normal epithelial melanocytes and share the lineage with retinal cells. cGMP-phosphodiesterase 6 (PDE6) is one of the cancer-retina antigens newly identified in melanoma cells. Normally, PDE6 hydrolyzes the photoreceptor second messenger cGMP allowing the visual signal transduction in photoreceptor cells. cGMP also play an important signaling role in stimulating melanogenesis in human melanocytes. Here, we present evidence that PDE6 is a key enzyme regulating the cGMP metabolism in melanoma cells. Decrease in intracellular cGMP leads to calcium accumulation in melanoma cells. In these cells, cGMP-phosphodiesterase 6 can be activated by another cancer-retina antigen, transducin, through Wnt5a-Frizzled-2 cascade, which leads to a lowering of cGMP and an increase in intracellular calcium mobilization. Thus, the aberrant expression of PDE6 may control cGMP metabolism and calcium homeostasis in melanoma cells.

Determination of the contribution of the myristoyl group and hydrophobic amino acids of recoverin on its dynamics of binding to lipid monolayers

It has been postulated that myristoylation of peripheral proteins would facilitate their binding to membranes. However, the exact involvement of this lipid modification in membrane binding is still a matter of debate. Proteins containing a Ca(2+)-myristoyl switch where the extrusion of their myristoyl group is dependent on calcium binding is best illustrated by the Ca(2+)-binding recoverin, which is present in retinal rod cells. The parameters responsible for the modulation of the membrane binding of recoverin are still largely unknown. This study was thus performed to determine the involvement of different parameters on recoverin membrane binding. We have used surface pressure measurements and PM-IRRAS spectroscopy to monitor the adsorption of myristoylated and nonmyristoylated recoverin onto phospholipid monolayers in the presence and absence of calcium. The adsorption curves have shown that the myristoyl group and hydrophobic residues of myristoylated recoverin strongly accelerate membrane binding in the presence of calcium. In the case of nonmyristoylated recoverin in the presence of calcium, hydrophobic residues alone are responsible for its much faster monolayer binding than myristoylated and nonmyristoylated recoverin in the absence of calcium. The infrared spectra revealed that myristoylated and nonmyristoylated recoverin behave very different upon adsorption onto phospholipid monolayers. Indeed, PM-IRRAS spectra indicated that the myristoyl group allows a proper orientation and organization as well as faster and stronger binding of myristoylated recoverin to lipid monolayers compared to nonmyristoylated recoverin. Simulations of the spectra have allowed us to postulate that nonmyristoylated recoverin changes conformation and becomes hydrated at large extents of adsorption as well as to estimate the orientation of myristoylated recoverin with respect to the monolayer plane. In addition, adsorption measurements and electrophoresis of trypsin-treated myristoylated recoverin in the presence of zinc or calcium demonstrated that recoverin has a different conformation but a similar extent of monolayer binding in the presence of such ions.

Photoreceptor proteins as cancer-retina antigens

Melanocytes, melanoma and photoreceptor cells are of neuroectodermal origin and have a certain sensitivity to light. In this study, we present evidence for photoreceptor proteins that are responsible for visual transduction and its regulation function as a new class of cancer antigens in melanoma. Visual rhodopsin, transducin, cGMP-phosphodiesterase 6, cGMP-dependent channels, guanylyl cyclase, rhodopsin kinase, recoverin and arrestin are expressed in melanoma and can induce antibody responses in patients. Melanocytes also express mRNA of all photoreceptor genes besides transducin, but were devoid of the corresponding protein, which was tested for rhodopsin, cGMP-phosphodiesterase, guanylyl cyclase and recoverin. Furthermore, we show for the first time that some healthy tissues express mRNA of these genes, but never protein. Expression profiles and autoantibody responses were confirmed in the MT/ret and the HGF(tg)/Ink4a(-/-) transgenic mouse melanoma models. We propose a molecular transition of cancer-retina antigens from mRNA expression in melanocytes to protein expression in melanoma. Our work provides the basis for analyzing regulation of photoreceptor gene expression in normal and malignant cells as well as possible therapeutic tumor targeting using the newly defined class of cancer-retina antigens.

Analysis of IgG antibody patterns against retinal antigens and antibodies to alpha-crystallin, GFAP, and alpha-enolase in sera of patients with "wet" age-related macular degeneration

BACKGROUND

The aim of this study was to compare the IgG antibody patterns against retinal antigens in sera of patients with age-related macular degeneration (AMD) and healthy subjects to learn more about possible immunological aspects of this disease and to identify some of the most important antigens.

METHODS

Sera of 140 patients were analyzed: healthy volunteers (CO, n=101) and patients with "wet" age-related macular degeneration (AMD, n=39). The sera were tested against western blots of bovine retinal antigens. The IgG antibody patterns were analyzed by multivariate statistical techniques and some antigens were identified via LC-MS/MS.

RESULTS

All patients showed complex patterns of IgG antibodies against retinal antigens. The discriminant analysis revealed a statistical significant difference between the antibody profiles of the AMD and the CO group (P=0.000023). Not only up-regulations of antigen-antibody-reactivities in the AMD group at some molecular weight ranges, e.g. at 46 and 52 kDa, could be seen, but also down-regulations, e.g. at 18 and 36 kDa. The 18 kDa antigen band was identified as alphaB-crystallin, the band at 46 kDa as alpha-enolase, and one at 52 kDa as glial fibrillary acidic protein.

CONCLUSIONS

We could demonstrate that both groups (wet AMD and CO) show complex IgG antibody patterns against retinal antigens, which are highly specific for each group. This provides further hints for the immunological basis of the disease. These changes in the antibody profiles in "wet" AMD could represent a secondary response to retinal damage or can play a causative role in the disease.