HR1

HR1 is an acronym used in several scientific and technical domains to denote different concepts. Because the meaning depends on context, articles that use the term typically specify the field and full form at first use.

In biology and medicine, HR1 most commonly refers to the histamine H1 receptor. This G-protein-coupled receptor is expressed in many tissues, including the brain, airways, and vascular endothelium. Activation of the receptor couples to Gq/11 signaling, triggering phospholipase C activity, production of inositol trisphosphate and diacylglycerol, and a rise in intracellular calcium. These events contribute to allergic and inflammatory responses such as itching, redness, bronchoconstriction, and increased vascular permeability. Antihistamine drugs that block H1 receptors are widely used to treat allergic rhinitis, urticaria, and related conditions.

In virology and structural biology, HR1 typically denotes heptad repeat 1, a segment of class I viral fusion proteins. In coronaviruses and some retroviruses, HR1 is part of the spike (or envelope) protein’s fusion machinery. Along with its partner HR2, HR1 forms a six-helix bundle that brings viral and cellular membranes into proximity, enabling fusion and entry. Disrupting the HR1–HR2 interaction, or using HR2-derived peptides, can inhibit infection in laboratory studies and is a focus of antiviral research.

Because HR1 has multiple meanings across disciplines, the intended interpretation should be inferred from the field and context.