Small Proline-Rich Protein 2A and 2D Are Regulated by the RBM38-p73 Axis and Associated with p73-Dependent Suppression of Chronic Inflammation

Small proline-rich protein 2A and 2D (SPRR2A and SPRR2D) provide barrier function in terminally differentiated stratified squamous epithelia through the epidermal differentiation complex. However, little is known how SPRR2A/2D expression is controlled and their role in chronic inflammation. Here, we showed that that SPRR2A/2D expression is controlled by a regulatory loop formed by RNA-binding protein RBM38 and tumor suppressor p73. Specifically, we found that SPRR2A/2D expression was induced by ectopic expression of RBM38 or p73 but suppressed by knockout of Rbm38 or p73. We also found that RBM38-mediated expression of SPRR2A/2D was p73-dependent and that induction of SPRR2A/2D during keratinocyte differentiation was dependent on both p73 and Rbm38. Additionally, we found that SPRR2A/2D expression was closely associated with p73 expression in normal and cancerous tissues. To determine the biological function of the RBM38-p73 loop potentially via SPRR2A/2D, we generated a cohort of wild-type, Rbm38−/−, Trp73+/−, and Rbm38−/−;Trp73+/− mice. We found that Rbm38−/−;Trp73+/− mice had a much shorter lifespan than that for Rbm38−/−—and to a lesser extent for Trp73+/− mice—but were less prone to spontaneous tumors than Trp73+/− or Rbm38−/− mice. We also found that Rbm38−/−;Trp73+/− mice exhibited weak expression of SPRR2A/2D in multiple tissues and were susceptible to systemic chronic inflammation, suggesting that decreased SPRR2A/2D expression is likely responsible for chronic inflammation in Rbm38−/−;Trp73+/− mice, leading to a shortened lifespan. Together, our data reveal that SPRR2A/2D are novel targets of the RBM38-p73 loop and contribute to p73-dependent suppression of chronic inflammation.

High Expression of SPRR1B Indicates Unfavorable Clinical Outcomes in Lung Adenocarcinoma

Backgrounds: Small proline-rich protein 1B (SPRR1B) was initially identified as an envelope protein of keratinocytes, which plays essential roles in squamous cell differentiation. Recently its involvement in malignancies was also explored in head and neck squamous cell carcinoma. However, whether SPRR1B participates in adenocarcinoma progression remains unknown. Here we aimed to investigate the expression and function of SPRR1B in lung adenocarcinoma (LAC).Methods: SPRR1B expression level was examined in LAC samples and adjacent nontumorous samples through quantitative RT-PCR assay and immunohistochemistry staining. Univariate and multivariate analyses were performed to estimate the prognostic role of SPRR1B. Cellular experiments were performed to reveal the function of SPRR1B in LAC cells. Results: The SPRR1B level in LAC samples was significantly higher compared with adjacent samples. Moreover, higher SPRR1B level was correlated with poor tumor differentiation and advanced tumor stage. LAC patients with higher SPRR1B level had worse overall survival. Moreover, SPRR1B was confirmed as an independent unfavorable prognosis factor. Cellular data indicated that knockdown of SPRR1B could attenuate the proliferation capacity of LAC cells. Conclusions: Our results demonstrated that high SPRR1B level was significantly correlated with unfavorable clinical features and poor prognosis of LAC patients. SPRR1B might serve as a novel prognostic indicator and potential drug target for LAC treatment.

Abstract 12788: Cardiac MicroRNA-150 Confers Cardioprotection by Directly Repressing Pro-apoptotic Small Proline-rich Protein 1a, Sprr1a in Cardiomyocytes

Background and Aims: Cardiac injury induces dynamic changes in the expression of microRNAs (miRs). For example, the evolutionarily conserved miR-150 is downregulated in patients with multiple cardiovascular diseases such as myocardial infarction (MI) and cardiomyopathies, as well as in various mouse models of heart failure (HF). MiR-150 is significantly associated with HF severity and outcome in humans. Using a systemic miR-150 knockout (KO) mouse model, we previously showed that carvedilol (Carv)/β 1 -adrenergic receptor/β-arrestin1-responsive miR-150 confers cardiac protection against MI (Left side in Figure). However, the extent to which expression of miR-150 in cardiomyocytes (CMs) regulates MI is unknown and there is a lack of mechanistic insight by which CM miR-150 modulates cardiac protection. Methods and Results: Here, we demonstrate using a novel mouse model that conditional CM-specific miR-150 KO (miR-150 cKO) in mice worsens cardiac dysfunction, stress, fibrosis and apoptosis post-MI, without affecting mortality or inflammation. Genome-wide transcriptomic analysis in miR-150 cKO mouse hearts identifies small proline-rich protein 1a (sprr1a) as a novel regulatory target of miR-150. Our mouse and CM studies further reveal that sprr1a expression is upregulated in CMs isolated from ischemic myocardium and subjected to simulated ischemia/reperfusion. In contrast, its expression is downregulated in hearts and CMs by Carv. Our human heart data also show that left ventricular sprr1a is upregulated in patients with HF with reduced ejection fraction. Mechanistically, the cardioprotective roles of CM miR-150 during MI are in part attributed to the direct and functional repression of pro-apoptotic gene sprr1a in CMs (Right side in Figure). Conclusions: These findings reveal a pivotal role for the miR-150/sprr1a axis in regulating CM function post-MI, and this novel axis could be a therapeutic target for intervention in ischemic heart disease.

Identification of SPRR3 as a novel diagnostic/prognostic biomarker for oral squamous cell carcinoma via RNA sequencing and bioinformatic analyses

Oral squamous cell carcinoma (OSCC) has always been one of the most aggressive and invasive cancers among oral and maxillofacial malignancies. As the morbidity and mortality of the disease have increased year by year, the search for a promising diagnostic and prognostic biomarker for the disease is becoming increasingly urgent. Tumorous and adjacent tissues were collected from three OSCC sufferers and we obtained 229 differentially expressed genes (DEGs) between tumor and normal tissues via high-throughput RNA sequence. Function and pathway enrichment analyses for DEGs were conducted to find a correlation between tumorigenesis status and DEGs. Protein interaction network and molecular complex detection (MCODE) were constructed to detect core modules. Two modules were enriched in MCODE. The diagnostic and prognostic values of the candidate genes were analyzed, which provided evidence for the candidate genes as new tumor markers. Small Proline Rich Protein 3 (SPRR3), a potential tumor marker that may be useful for the diagnosis of OSCC, was screened out. The survival analysis showed that SPRR3 under expression predicted the poor prognosis of OSCC patients. Further experiments have also shown that the expression of SPRR3 decreased as the malignancy of OSCC increased. Therefore, we believe that SPRR3 could be used as a novel diagnostic and prognostic tumor marker.

Small proline-rich protein 2B drives stress-dependent p53 degradation and fibroblast proliferation in heart failure

Heart disease is associated with the accumulation of resident cardiac fibroblasts (CFs) that secrete extracellular matrix (ECM), leading to the development of pathological fibrosis and heart failure. However, the mechanisms underlying resident CF proliferation remain poorly defined. Here, we report that small proline-rich protein 2b (Sprr2b) is among the most up-regulated genes in CFs during heart disease. We demonstrate that SPRR2B is a regulatory subunit of the USP7/MDM2-containing ubiquitination complex. SPRR2B stimulates the accumulation of MDM2 and the degradation of p53, thus facilitating the proliferation of pathological CFs. Furthermore, SPRR2B phosphorylation by nonreceptor tyrosine kinases in response to TGF-β1 signaling and free-radical production potentiates SPRR2B activity and cell cycle progression. Knockdown of the Sprr2b gene or inhibition of SPRR2B phosphorylation attenuates USP7/MDM2 binding and p53 degradation, leading to CF cell cycle arrest. Importantly, SPRR2B expression is elevated in cardiac tissue from human heart failure patients and correlates with the proliferative state of patient-derived CFs in a process that is reversed by insulin growth factor-1 signaling. These data establish SPRR2B as a unique component of the USP7/MDM2 ubiquitination complex that drives p53 degradation, CF accumulation, and the development of pathological cardiac fibrosis.