Immunohistochemical Examination of Induced Both a-Crystallin and Ubiquitin Activities in the Human Lens

Abstract

Stress induces the synthesis of several large and small heat shock proteins (hsp). In our study we planned to investigate two small hsps, a-crystallin and ubiquitin, in human lenses removed patients with mature senile cataract. Conjugation of ubiquitin, a small hsp, to some proteins appears to be required for the initiation of their degradation by cellular proteases. a-B crystallin is an abundant protein in several tissues, particularly high amounts of which accumulate in the lens. Recently, it has been shown that lens a- crystallins are substrates for ubiquitin-dependent degradation. Here we immunohistochemically show that lenses operated on due to matured senile cataract have increased activity of a-B crystallin and ubiquitin. The lens protein a-B crystallin accomplishes a structural role in maintaining lens stability and transparency. With age or for other reasons, increased amounts of the protein might change the stability of the lens, and this increased amount of the protein can not be degraded by the ubiquitin system since the system is saturated. Therefore, these events might contribute cataract formation.