Hook-associated protein 2 (HAP2) (HAP2)

Hook-associated protein 2 (HAP2), also known as Generative cell-specific protein 1 (GCS1), is a highly conserved membrane protein essential for gamete fusion across diverse eukaryotic lineages, including plants, protists, and invertebrates (UniProt Q8I4V7). In the context of human health, HAP2 is a primary target for transmission-blocking vaccines (TBVs) against malaria-causing parasites like Plasmodium falciparum (Angrisano et al., 2017, BMC Biology). Structurally, HAP2 is classified as a Class II viral-like fusogen, sharing significant homology with fusion proteins found in viruses such as Dengue and Zika (Fedry et al., 2017, Cell). It is specifically expressed on the surface of male gametes, where it facilitates the merger of the male and female plasma membranes during fertilization in the mosquito midgut (Pinello et al., 2017, JBC). Therapeutic strategies focus on inducing antibodies that bind to the extracellular domain of HAP2, thereby neutralizing the parasite's ability to reproduce sexually and preventing the spread of infection to new hosts. Because HAP2 is absent in mammals, it represents a highly specific target with a low risk of off-target effects in humans.

Other names

Generative cell-specific protein 1GCS1HAP2/GCS1HAP2 homologue

Inhibition of gamete fusion by binding to the extracellular domain of HAP2 on male gametes, preventing the merger of male and female plasma membranes during the sexual stage of the parasite life cycle (Fedry et al., 2017, Cell).