1,440 articles
Propofol infusion syndrome
Propofol infusion syndrome (PRIS), a rare potentially fatal complication of high-dose (>5 mg/kg/h) or prolonged (>48 h) propofol sedation, marked by metabolic acidosis, rhabdomyolysis, ECG changes, and mitochondrial fatty-acid oxidation failure.
Protease-activated receptor 2
Protease-activated receptor 2 (PAR2, F2RL1) is a GPCR activated by proteolytic cleavage exposing a tethered ligand (SLIGKV); the only thrombin-insensitive PAR, activated by trypsin and tryptase, linked to inflammation, pain, and cancer drug development.
Protein DPCD
Protein DPCD (deleted in primary ciliary dyskinesia homolog; HGNC 24542, UniProt Q9BVM2) is a 203-amino-acid ciliary protein linked to ciliogenesis, R2TP/Akt signaling, and PCD candidate status, distinct from the FDA's Division of Patient-Centered Development.
Protein localization
Protein localization: cellular processes establishing and maintaining proteins at specific subcellular sites via targeting motifs, SRP and translocase pathways; mislocalization drives disease and is now a therapeutic target.
Protein sepa-1
Protein sepa-1 (SEPA-1, suppressor of ectopic P granule in autophagy mutants-1) is a C. elegans selective autophagy receptor that self-oligomerizes, binds PGL-3 and LGG-1, and mediates ubiquitin-independent degradation of P granule components in embryos.
Protein synthesis inhibitor
Protein synthesis inhibitors are compounds, usually antibiotics or toxins, that block translation. Key classes target the 30S or 50S ribosomal subunit; first bacterial reports date to 1950, first eukaryotic report (cycloheximide) to 1958.
Protein tagging
Protein tagging is a bench biology method that attaches a detectable label to a protein of interest, either genetically or chemically, to report its location and interactions.
Protein Transport
Protein transport (protein trafficking, protein sorting): movement of proteins between cellular compartments via gated transport, transmembrane translocation, and vesicular transport, guided by sorting signals; Blobel's signal hypothesis won the 1999 Nobel Prize.
Protein transport protein Sec23
Sec23 (SEC23A/SEC23B in mammals) is the inner-coat COPII protein and Sar1 GAP that drives ER-to-Golgi vesicle transport; mutations cause CLSD and CDAII.
Protein transport protein Sec24
Sec24 (SEC24A–D in humans) is the cargo-selection subunit of the COPII coat, binding ER export signals to package proteins for ER-to-Golgi transport; four paralogs in A/B and C/D subgroups have overlapping but distinct cargo preferences.
Proteostasis
Proteostasis (protein homeostasis) is the cellular regulation of protein concentration, folding, interactions, localization, and degradation via the proteostasis network of chaperones, the ubiquitin-proteasome system, and autophagy; its decline underlies aging and proteinopathies.
Proton pump
Proton pump: membrane protein using ATP to move H+ across membranes. Covers the rotary V-ATPase (V1/V0 domains, organelle acidification) and the gastric H+/K+-ATPase targeted by PPIs and vonoprazan.
Protoplasm
Protoplasm: the living contents of a cell, cytoplasm plus nucleoplasm; term coined by Purkinje (1839/1840), popularized by von Mohl (1846), basis of 19th-century protoplasm theory, now obsolete in technical use.
Protoplasma
Protoplasma is an Austrian peer-reviewed cell biology journal founded in 1926, published by Springer Vienna, covering animal, fungal, and plant cell biology, with ISSN 0033-183X and a 2025 impact factor of 2.7.
Protoplasmic astrocyte
Protoplasmic astrocyte: the gray-matter astrocyte class (versus fibrous astrocytes), with fine perisynaptic processes ensheathing synapses, glutamate and potassium clearance, nonoverlapping domains covering up to 2 million synapses in humans.
Protoplast
Protoplast: a plant cell stripped of its cell wall (term from Hanstein, 1880). Isolated enzymatically since Cocking 1960; totipotent, used for transformation, fusion, CRISPR editing, and single-cell sequencing.
Proximity labeling
Proximity labeling is a molecular biology technique in which an engineered enzyme fused to a protein of interest tags nearby proteins in living cells for mass spectrometry.
Pseudopodia
Pseudopodia (pseudopods, "false feet") are temporary actin-rich cell-surface extensions used by amoebae, neutrophils, and other eukaryotic cells for locomotion and food capture, driven by actin polymerization and organized by chemotactic signaling.
Pulmonary alveolar type 1 cell
Pulmonary alveolar type 1 cell (AT1, type I pneumocyte): flattened squamous epithelial cell covering over 95% of the alveolar surface, forming the thin air-blood barrier for gas exchange, marked by AQP5, PDPN, AGER, HOPX, and largely renewed from AT2 cells after injury.
Pulmonary alveolar type 2 cell
Pulmonary alveolar type 2 cell (AT2, type II pneumocyte): cuboidal surfactant-secreting alveolar epithelial cell with lamellar bodies, covering about 5% of alveolar surface, acting as the adult distal lung stem cell that renews AT1 cells.
Pulmonary neuroendocrine cell
Pulmonary neuroendocrine cells (PNECs), also called helle Zellen or bright cells, are rare innervated airway epithelial cells (0.4% of airway epithelium) that form neuroepithelial bodies at airway branch points, sense hypoxia, secrete CGRP and serotonin, and are the cell of origin of small cell lung cancer.
Pulse labeling
Pulse labeling is a cell biology technique that briefly exposes cells to a labeled precursor, such as a radioactive nucleotide, marking molecules synthesized during that interval.
Pure mitochondrial myopathy
Pure mitochondrial myopathy is a rare mitochondrial disorder affecting only skeletal muscle, causing progressive limb weakness, muscle wasting, and eye muscle problems such as ptosis.
Puromycin
Puromycin, an aminonucleoside antibiotic from Streptomyces alboniger that mimics aminoacyl-tRNA and prematurely terminates translation; not used clinically but central to SUnSET, OPP nascent proteomics, and ribosome profiling.
Pyroptosis
Pyroptosis: lytic, inflammatory programmed cell death executed by gasdermin D pores after caspase-1/4/5/11 activation, releasing IL-1β and DAMPs; distinct from apoptosis and necroptosis, involved in infection defense, inflammation, and cancer.
Pyruvate carboxylase
Pyruvate carboxylase (PC, EC 6.4.1.1), pyruvic carboxylase, is a biotin-dependent mitochondrial tetrameric enzyme converting pyruvate to oxaloacetate for gluconeogenesis, lipogenesis, and insulin secretion; PC gene mutations cause autosomal recessive pyruvate carboxylase deficiency.
Pyruvate dehydrogenase complex
Pyruvate dehydrogenase complex (PDC, PDHc): mitochondrial multi-enzyme assembly (E1, E2, E3, 5-12 MDa) converting pyruvate to acetyl-CoA, CO2, and NADH; regulated by PDK/PDP phosphorylation; deficient in PDC deficiency and dysregulated in cancer.
Q cycle
Q cycle: Mitchell's 1975 mechanism for cytochrome bc1 (complex III) and b6f complexes, in which bifurcated quinol oxidation at the Qo site and quinone recycling at the Qi site pump protons to build a proton motive force.
Quantitative immunofluorescence
Quantitative immunofluorescence is a microscopy method that measures fluorescence intensity from antibody-labeled targets to quantify protein abundance, localization, and expression differences in cells and tissues.
R7 photoreceptor cell
R7 photoreceptor cell (R7 cell, CL:0000707) is the distal inner photoreceptor of each Drosophila ommatidium, UV-sensitive via Rh3 or Rh4, specified by Sevenless/Boss and Notch signaling, projecting to medulla layer M6 for color vision.