Association of Hsp47, Grp78, and Grp94 with procollagen supports the successive or coupled action of molecular chaperones

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Abstract
Hps47, Grp78, have been implicated with procellagen maturation events. In particular Hps47 has been shown to blind to nascent procellagen α1(I) chains in the course of synthesis and/or translocation into the endoplasmic reticulum (ER). Although, Hsp47 binding to gelatin and collgen has previsously been suggested to mechanism. The early association of Hps47 with procollagen and its relatively late relese suggested that other chaperones, Grp78 and Grp94, interact successively or concurrently with Hps47. Herein, we examined how these events occurs in cells metabolically stressed by depletion of ATP. In cells depleted of ATP, the releses of Hps47, Grp78, and Grp94 from maturing procollange is delayed. Thus, in cell experiencing metabolic stress, newly synthesized procollagen unable to property fold became stable bound to a complex of molecular chaperones. In that Hps47, Grp78, and Grp98 could be recovered with nascent procollagen and as oligomer in ATP depleted cells suggests that these chaperones function in a series of coupled or successive reactions.