May contribute to the transparency and refractive index of the lens. Has chaperone-like activity, preventing aggregation of various proteins under a wide range of stress conditions. In lens epithelial cells, stabilizes the ATP6V1A protein, preventing its degradation by the proteasome (PubMed:31786107). Heteromer composed of three CRYAA and one CRYAB subunits. Aggregates with homologous proteins, including the small heat shock protein HSPB1, to form large heteromeric complexes. Inter-subunit bridging via zinc ions enhances stability, which is crucial as there is no protein turn over in the lens (By similarity). Interacts with HSPBAP1 (PubMed:10751411). Interacts with TTN/titin. Interacts with TMEM109. Interacts with DES; binds rapidly during early stages of DES filament assembly and a reduced binding seen in the later stages. Interacts with TMED10; the interaction mediates the translocation from the cytoplasm into the ERGIC (endoplasmic reticulum-Golgi intermediate compartment) and thereby secretion (By similarity). Interacts with ATP6V1A and with MTOR, forming a ternary complex (PubMed:31786107). Translocates to the nucleus during heat shock and resides in sub-nuclear structures known as SC35 speckles or nuclear splicing speckles. Localizes at the Z-bands and the intercalated disk in cardiomyocytes. Can be secreted; the secretion is dependent on protein unfolding and facilitated by the cargo receptor TMED10; it results in protein translocation from the cytoplasm into the ERGIC (endoplasmic reticulum-Golgi intermediate compartment) followed by vesicle entry and secretion. Lens as well as other tissues. Up-regulated by HSF4. Belongs to the small heat shock protein (HSP20) family.