Ceapins block the unfolded protein response sensor ATF6α by inducing a neomorphic inter-organelle tether

The unfolded protein response (UPR) detects and restores deficits in the endoplasmic reticulum (ER) protein folding capacity. Ceapins specifically inhibit the UPR sensor ATF6α, an ER-tethered transcription factor, by retaining it at the ER through an unknown mechanism. Our genome-wide CRISPR interference (CRISPRi) screen reveals that Ceapins function is completely dependent on the ABCD3 peroxisomal transporter. Proteomics studies establish that ABCD3 physically associates with ER-resident ATF6α in cells and in vitro in a Ceapin-dependent manner. Ceapins induce the neomorphic association of ER and peroxisomes by directly tethering the cytosolic domain of ATF6α to ABCD3’s transmembrane regions without inhibiting or depending on ABCD3 transporter activity. Thus, our studies reveal that Ceapins function by chemical-induced misdirection which explains their remarkable specificity and opens up new mechanistic routes for drug development and synthetic biology.

Twenty-four-hour progesterone and luteinizing hormone profiles in the midluteal phase of the infertile patient: correlation with other indicators of luteal phase insufficiency

The authors have further analyzed women diagnosed as having luteal phase insufficiency in hope of determining the value of specific screening tests as well as determining the degree of heterogeneity of pathophysiologic mechanisms involved in the disorder. Twelve women with the disorder were identified, 6 with two consecutive midluteal serum progesterone (P) levels less than 10 ng/ml (group 1) and 6 with two consecutive late luteal phase endometrial biopsies out of phase (group 2); 4 infertile women with normal serum P and late luteal biopsies also were studied (group 3). All underwent serum sampling for P and luteinizing hormone (LH) at 20-minute intervals for 24 hours, beginning at 9:00 A.M. of day 7 post-LH surge. No significant differences were noted among the three groups for LH area under the curve, pulse frequency, or pulse amplitude. Furthermore, no differences were ascertained for P area under the curve. However, individuals were identified who had one or more hormonal abnormalities but no abnormal biopsy, as well as patients with normal hormonal profiles but having abnormal endometrial development. Receiver Operating Characteristic curves demonstrated that pooled morning serum P levels provided optimal predictive ability of biopsy results. The authors conclude that luteal phase insufficiency is a heterogeneous disorder, and that neither endometrial biopsy nor serum hormonal analysis obviates the need for the other.