Intracellular proteins are targeted for proteolytic degradation in the lysosome with the aid of chaperones. Heat shock cognate 71 kDa protein (HSPA8) acts as the constitutive chaperone that binds KFERQ-domain containing substrates in the cytosol. Consequently, the Hspa8:Substrate complex translocates from cytosol to lysosomal membrane where it binds to Lysosome-associated membrane glycoprotein 2 (LAMP2a). Subsequently, HSPA8 is released and Heat shock protein HSP 90 binds to the lysosomal luminal end of LAMP2a. Binding of HSP90 stabilizes LAMP2 to multimerize into a 700 kDa complex (Bandyopadhyay U et al. 2008). This facilitates the internalization of substrate into the lumen. Experiments confirming this binding were performed on rat models.
Cuervo, AM, Kaushik, S, Bandyopadhyay, U, Varticovski, L
Cuervo, AM, Kiffin, R, Sridhar, S, Kaushik, S, Bandyopadhyay, U
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