Enables complement component C3a binding activity and complement component C3a receptor activity. Involved in several processes, including positive regulation of DNA biosynthetic process; positive regulation of cell population proliferation; and tolerance induction to nonself antigen. Located in plasma membrane. Used to study adult respiratory distress syndrome. Biomarker of asthma and lung disease. Human ortholog(s) of this gene implicated in asthma. Orthologous to human C3AR1 (complement C3a receptor 1). [provided by Alliance of Genome Resources, Apr 2022]