Functions and pathologies of BiP and its interaction partners.

The endoplasmic reticulum (ER) is involved in a variety of essential and interconnected processes in human cells, including protein biogenesis, signal transduction, and calcium homeostasis. The central player in all these processes is the ER-lumenal polypeptide chain binding protein BiP that acts as a molecular chaperone. BiP belongs to the heat shock protein 70 (Hsp70) family and crucially depends on a number of interaction partners, including co-chaperones, nucleotide exchange factors, and signaling molecules. In the course of the last five years, several diseases have been linked to BiP and its interaction partners, such as a group of infectious diseases that are caused by Shigella toxin producing E. coli. Furthermore, the inherited diseases Marinesco-Sjögren syndrome, autosomal dominant polycystic liver disease, Wolcott-Rallison syndrome, and several cancer types can be considered BiP-related diseases. This review summarizes the physiological and pathophysiological characteristics of BiP and its interaction partners.

AM representation in green treefrog auditory nerve fibers: neuroethological implications for pattern recognition and sound localization.

In addition to spectral call components, temporal patterns in the advertisement-call envelope of green treefrog males ( Hyla cinerea) provide important cues for female mate choice. Rapid amplitude modulation (AM) with rates of 250-300 Hz is typical for this species' advertisement calls. Here we report data on the encoding of these rapid call modulations by studying the responses of single auditory nerve fibers to two-tone stimuli with envelope periodicities close to those of the natural call. The free-field response properties of 86 nerve fibers were studied from 32 anesthetized males. The accuracy of stimulus envelope coding was quantified using both a Gaussian function fit to the interspike interval histograms derived from the first seven 20-ms stimulus segments, and the vector-strength metric applied to the phase-locked responses. Often, AM encoding in the initial stimulus segment was more faithful than that in its second half. This result may explain why conspecific females prefer calls in which the initial segment is unmasked rather than masked. Both the questions of pattern recognition and localization are discussed, and the data are related to behavioral observations of female choice and localization performance in this species.

Temperature dependence of two-tone rate suppression in the northern leopard frog, Rana pipiens pipiens.

The existence region of two-tone rate suppression in frog low-frequency auditory-nerve fibers was found to include a suppressive region below a fiber's characteristic frequency, contrary to previous reports. In response to 3 degrees C rise in core temperature, the area and the best suppressive frequency (BSF) of the low-side suppressive region significantly increased. Increasing core temperature of the frog by 6 degrees C resulted in significant changes in the high-side suppressive region: Its area decreased, and its BSF and best suppressive threshold (BST) increased. Constant-temperature control trials were designed to partially simulate the relative movement of the probe tone within the excitatory tuning curve which occurred during temperature shifts. Lowering the probe tone by 0.5 oct had no effect on the low-side suppressive region, but significantly increased the area and lowered the BSF and BST of the high-side suppressive region. Temperature shifts in the frog appear to have a differential effect on the low-side and high-side suppressive areas of low-frequency auditory-nerve fibers. Moreover, excitation and suppression also respond differentially to temperature shifts.

CALLING SONG DISPLACEMENT IN A ZONE OF OVERLAP AND HYBRIDIZATION.

The ground crickets Allonemobius fasciatus and A. socius meet in a mosaic zone of overlap and hybridization stretching from the East Coast to at least Illinois. To test whether male calling song differences were enhanced in sympatry, we analyzed the songs of crickets from inside and outside the zone of overlap along two transects. No evidence of calling song displacement was found in A. socius males from populations within the zone of overlap. On the other hand, A. fasciatus displayed calling song displacement in three populations. Our results are consistent with the hypothesis that the selective pressure exerted by the challenge from a related species is frequency dependent. While not a conclusive demonstration, the observed shifts in calling song are strongly suggestive of reproductive character displacement.