Chaperone properties of Pdia3 participate in rapid membrane actions of 1α,25-dihydroxyvitamin D3.

Mol Endocrinol. 2013 May 9;

Authors: Chen J, Lobachev KS, Grindel BJ, Farach-Carson MC, Hyzy SL, El-Baradie KB, Olivares-Navarrete R, Doroudi M, Boyan BD, Schwartz Z

Abstract
Protein disulfide isomerase family A, member 3 (Pdia3) mediates many of the plasma membrane (PM) associated rapid responses to 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3). It is not well understood how Pdia3, which is an endoplasmic reticulum (ER) chaperone, functions as a PM receptor for 1α,25(OH)2D3. We mutated three amino acids (K214 and R282 in the calreticulin interaction site and C406 in the isomerase catalytic site), which are important for Pdia3's ER chaperone function, and examined their role in responses to 1α,25(OH)2D3. Pdia3 constructs with and without the ER retention signal KDEL were used to investigate the PM requirement for Pdia3. Finally, we determined if palmitoylation and/or myristoylation were required for Pdia3-mediated responses to 1α,25(OH)2D3. Overexpressing the Pdia3 R282A mutant in MC3T3-E1 cells increased PM phospholipase A2 activating protein (PLAA), c-Src, and caveolin-1, but blocked increases in 1α,25(OH)2D3-stimulated protein kinase C (PKC) seen in cells overexpressing wild-type Pdia3 (Pdia3Ovr cells). Cells overexpressing Pdia3 with K214A and C406S mutations had PKC activity comparable to untreated controls indicating that the native response to 1α,25(OH)2D3 also was blocked. Overexpressing Pdia3[-KDEL] increased PM localization and augmented baseline PKC but the stimulatory effect of 1α,25(OH)2D3 was comparable to that seen in wild-type cultures. In contrast, 1α,25(OH)2D3 increased PGE2 in Pdia3[±KDEL] cells. While neither palmitoylation nor myristoylation was required for PM association of Pdia3, myristoylation was needed for PKC activation. These data indicate that both the chaperone functional domains and the subcellular location of Pdia3 control rapid membrane responses to 1α,25(OH)2D3.

PMID: 23660595 [PubMed - as supplied by publisher]

When secondary comes first - The importance of non-canonical DNA structures.

Biochimie. 2012 Oct 16;

Authors: Saini N, Zhang Y, Usdin K, Lobachev KS

Abstract
Secondary structure-forming DNA motifs have achieved infamy because of their association with a variety of human diseases and cancer. The 3rd FASEB summer conference on dynamic DNA structures focused on the mechanisms responsible for the instabilities inherent to repetitive DNA and presented many exciting and novel aspects related to the metabolism of secondary structures. In addition, the meeting encompassed talks and posters on the dynamic structures that are generated during DNA metabolism including nicked DNA, Holliday junctions and RNA:DNA hybrids. New approaches for analysis and sequencing technologies put forth secondary structures and other DNA intermediates as vital regulators of a variety of cellular processes that contribute to evolution, polymorphisms and diseases.

PMID: 23084930 [PubMed - as supplied by publisher]