Alpha-crystallin A chain (HSPB4) (HSPB4)

Alpha-crystallin A chain (HSPB4) is a small heat shock protein (sHSP) that primarily functions as a molecular chaperone to maintain protein solubility and prevent the aggregation of denatured proteins [1, 3]. In the ocular lens, it forms large, dynamic hetero-oligomeric complexes with its partner HSPB5 (Alpha-crystallin B chain), which are essential for maintaining lens transparency and refractive power [1, 6]. Beyond its structural role, HSPB4 acts as a damage-associated molecular pattern (DAMP) when released from necrotic or injured cells, particularly in the cornea [2]. In this capacity, it interacts with Toll-like receptor 2 (TLR2) on resident macrophages to trigger a pro-inflammatory cascade involving NF-κB and the production of cytokines like IL-1β and IL-6 [2, 4]. Therapeutic interest in HSPB4 focuses on two main areas: restoring its chaperone activity or solubility to treat cataracts using small molecules like lanosterol and VP1-001, and inhibiting its DAMP-mediated inflammatory signaling to treat ocular surface diseases and sterile inflammation using agents like TSG-6 or neutralizing antibodies [2, 3, 5]. Mutations in the HSPB4 gene are also a known cause of congenital cataracts, highlighting its critical role in proteostasis [1, 6].

Other names

CRYAAAlpha-A-crystallinHeat shock protein beta-4Alpha-crystallin AHSPB4-HSPB5 hetero-oligomerAlpha-crystallin complex

Acts as a molecular chaperone to prevent protein aggregation and maintain solubility; also functions as a damage-associated molecular pattern (DAMP) that activates TLR2-mediated inflammatory signaling.