Mutation in Phospholipase C, δ1 (PLCD1) Gene Underlies Hereditary Leukonychia in a Pashtun Family and Review of the Literature

Activation Mechanisms and Diverse Functions of Mammalian Phospholipase C

Phospholipase C (PLC) plays pivotal roles in regulating various cellular functions by metabolizing phosphatidylinositol 4,5-bisphosphate in the plasma membrane. This process generates two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol, which respectively regulate the intracellular Ca²⁺ levels and protein kinase C activation. In mammals, six classes of typical PLC have been identified and classified based on their structure and activation mechanisms. They all share X and Y domains, which are responsible for enzymatic activity, as well as subtype-specific domains. Furthermore, in addition to typical PLC, atypical PLC with unique structures solely harboring an X domain has been recently discovered. Collectively, seven classes and 16 isozymes of mammalian PLC are known to date. Dysregulation of PLC activity has been implicated in several pathophysiological conditions, including cancer, cardiovascular diseases, and neurological disorders. Therefore, identification of new drug targets that can selectively modulate PLC activity is important. The present review focuses on the structures, activation mechanisms, and physiological functions of mammalian PLC.

Morphine disrupts macrophage functions even during HIV infection

HIV-associated neurocognitive impairment (HIV-NCI) is a debilitating comorbidity that reduces quality of life in 15-40% of people with HIV (PWH) taking antiretroviral therapy (ART). Opioid use has been shown to increase neurocognitive deficits in PWH. Monocyte-derived macrophages (MDMs) harbor HIV in the CNS even in PWH on ART. We hypothesized that morphine (MOR), a metabolite of heroin, further dysregulates functional processes in MDMs to increase neuropathogenesis. We found that, in uninfected and HIV-infected primary human MDMs, MOR activates these cells by increasing phagocytosis and up-regulating reactive oxygen species. Effects of MOR on phagocytosis were dependent on μ-opioid receptor activity and were mediated, in part, by inhibited lysosomal degradation of phagocytized substrates. All results persisted when cells were treated with both MOR and a commonly prescribed ART cocktail, suggesting minimal impact of ART during opioid exposure. We then performed mass spectrometry in HIV-infected MDMs treated with or without MOR to determine proteomic changes that suggest additional mechanisms by which opioids affect macrophage homeostasis. Using downstream pathway analyses, we found that MOR dysregulates ER quality control and extracellular matrix invasion. Our data indicate that MOR enhances inflammatory functions and impacts additional cellular processes in HIV-infected MDMs to potentially increases neuropathogenesis in PWH using opioids.

Leukonychia: What Can White Nails Tell Us?

Changes in nail color can provide important clues of underlying systemic and skin disease. In particular, white discoloration (leukonychia) has a high prevalence with a wide array of potential relevant causes, from simple manicure habits to life-threatening liver or kidney failure. Therefore, a reliable assessment of the patient with leukonychia is essential. In the past, two classifications for leukonychia have been presented. The morphological classifies the nail according to the distribution of the white lines: total, partial, transversal, and longitudinal leukonychia. Mees’ and Muehrcke’s lines are examples of transversal leukonychia, while Terry’s and Lindsay’s nails are examples of total and partial leukonychia. The anatomical classifies according to the structure responsible for the white color: the nail plate in true leukonychia, the nail bed in apparent leukonychia, and the surface only in pseudoleukonychia. In this review, both morphological and anatomical features have been combined in an algorithm that enables clinicians to approach leukonychia efficiently and effectively.

Phospholipase C families: Common themes and versatility in physiology and pathology

Phosphoinositide-specific phospholipase Cs (PLCs) are expressed in all mammalian cells and play critical roles in signal transduction. To obtain a comprehensive understanding of these enzymes in physiology and pathology, a detailed structural, biochemical, cell biological and genetic information is required. In this review, we cover all these aspects to summarize current knowledge of the entire superfamily. The families of PLCs have expanded from 13 enzymes to 16 with the identification of the atypical PLCs in the human genome. Recent structural insights highlight the common themes that cover not only the substrate catalysis but also the mechanisms of activation. This involves the release of autoinhibitory interactions that, in the absence of stimulation, maintain classical PLC enzymes in their inactive forms. Studies of individual PLCs provide a rich repertoire of PLC function in different physiologies. Furthermore, the genetic studies discovered numerous mutated and rare variants of PLC enzymes and their link to human disease development, greatly expanding our understanding of their roles in diverse pathologies. Notably, substantial evidence now supports involvement of different PLC isoforms in the development of specific cancer types, immune disorders and neurodegeneration. These advances will stimulate the generation of new drugs that target PLC enzymes, and will therefore open new possibilities for treatment of a number of diseases where current therapies remain ineffective.