The profile of expression of the scaffold protein SG2NA(s) differs between cancer types and its interactome in normal vis-a-vis breast tumor tissues suggests its wide roles in regulating multiple cellular pathways

Cellular Impacts of Striatins and the STRIPAK Complex and Their Roles in the Development and Metastasis in Clinical Cancers (Review)

Striatins (STRNs) are generally considered to be cytoplasmic proteins, with lower expression observed in the nucleus and at cell-cell contact regions. Together with protein phosphatase 2A (PP2A), STRNs form the core region of striatin-interacting phosphatase and kinase (STRIPAK) complexes through the coiled-coil region of STRN proteins, which is crucial for substrate recruitment. Over the past two decades, there has been an increasing amount of research into the biological and cellular functions of STRIPAK members. STRNs and the constituent members of the STRIPAK complex have been found to regulate several cellular functions, such as cell cycle control, cell growth, and motility. Dysregulation of these cellular events is associated with cancer development. Importantly, their roles in cancer cells and clinical cancers are becoming recognised, with several STRIPAK components found to have elevated expression in cancerous tissues compared to healthy tissues. These molecules exhibit significant diagnostic and prognostic value across different cancer types and in metastatic progression. The present review comprehensively summarises and discusses the current knowledge of STRNs and core STRIPAK members, in cancer malignancy, from both cellular and clinical perspectives.

A novel STRN3::PRKD1 fusion in a cribriform adenocarcinoma of salivary gland with high-grade transformation

Cribriform adenocarcinoma of salivary gland (CASG) is a rare form of salivary gland neoplasm that mostly arises from minor salivary glands. We report a case of CASG with high-grade transformation harboring a novel STRN3::PRKD1 fusion. A 59-year-old male presented with a palatal mass. Morphologically, the tumor consisted of two components: solid high-grade and glandular low-grade areas. The solid high-grade area comprised solid nests of high-grade carcinoma with central necrosis arranged in lobules delineated with prominent stromal septa. The glandular low-grade area comprised of cribriform and microcystic architecture in a hyalinized and hypocellular stroma. Immunophenotypically, the tumor was positive for S100 but negative for p40 and actin. However, due to the high-grade component, tissue was sent for salivary gland NGS fusion panel analysis to confirm the diagnosis. The current case illustrates high-grade transformation in CASG. Furthermore, identification of a STRN3::PRKD1 fusion expands the genetic spectrum of CASG.

Striatin family proteins: The neglected scaffolds

The Striatin family of proteins constitutes Striatin, SG2NA, and Zinedin. Members of this family of proteins act as a signaling scaffold due to the presence of multiple protein-protein interaction domains. At least two members of this family, namely Zinedin and SG2NA, have a proven role in cancer cell proliferation. SG2NA, the second member of this family, undergoes alternative splicing and gives rise to several isoforms which are differentially regulated in a tissue-dependent manner. SG2NA evolved earlier than the other two members of the family, and SG2NA undergoes not only alternative splicing but also other posttranscriptional gene regulation. Striatin also undergoes alternative splicing, and as a result, it gives rise to multiple isoforms. It has been shown that this family of proteins plays a significant role in estrogen signaling, neuroprotection, cancer as well as in cell cycle regulation. Members of the striatin family form a complex network of signaling hubs with different kinases and phosphatases, and other signaling proteins named STRIPAK. Here, in the present manuscript, we thoroughly reviewed the findings on striatin family members to elaborate on the overall structural and functional idea of this family of proteins. We also commented on the involvement of these proteins in STRIPAK complexes and their functional relevance.