[Therapy of esophageal motility disorders]. / Therapieoptionen von primären Motilitätsstörungen des Ösophagus.

Esophageal motility disorders are diseases in which there are malfunctions of the act of swallowing due to a change in neuromuscular structures. The main symptom is therefore dysphagia for solid and/or liquid foods, often accompanied by symptoms such as chest pain, regurgitation, heartburn, and weight loss. Esophageal manometry is the gold standard in diagnostics. Endoscopy and radiology serve to exclude inflammatory or malignant changes. With the introduction of high-resolution esophageal manometry (HRM), the diagnosis of esophageal motility disorders has improved and led to a new classification with the Chicago Classification, which has been modified several times in the last decade, most recently in 2020 with the Chicago Classification v4.0. Compared to the previous version 3.0, there are some important changes that are presented based on the most important esophageal motility disorders in everyday clinical practice.

[Diagnosis of esophageal motility disorders - Significance of the new Chicago classification v4.0]. / Diagnostik von Motilitätsstörungen des Ösophagus ­ Bedeutung der neuen Chicago-Klassifikation v4.0.

Esophageal motility disorders are diseases in which there are malfunctions of the act of swallowing due to a change in neuromuscular structures. The main symptom is therefore dysphagia for solid and/or liquid foods, often accompanied by symptoms such as chest pain, regurgitation, heartburn, and weight loss. Esophageal manometry is the gold standard in diagnostics. Endoscopy and radiology serve to exclude inflammatory or malignant changes. With the introduction of high-resolution esophageal manometry (HRM), the diagnosis of esophageal motility disorders has improved and led to a new classification with the Chicago Classification, which has been modified several times in the last decade, most recently in 2021 with the Chicago Classification v4.0. Compared to the previous version 3.0, there are some important changes that are presented based on the most important esophageal motility disorders in everyday clinical practice.

[Diagnosis of esophageal motility disorders - Significance of the new Chicago classification v4.0]. / Diagnostik von Motilitätsstörungen des Ösophagus ­ Bedeutung der neuen Chicago-Klassifikation v4.0.

Esophageal motility disorders are diseases in which there are malfunctions of the act of swallowing due to a change in neuromuscular structures. The main symptom is therefore dysphagia for solid and/or liquid foods, often accompanied by symptoms such as chest pain, regurgitation, heartburn, and weight loss. Esophageal manometry is the gold standard in diagnostics. Endoscopy and radiology serve to exclude inflammatory or malignant changes. With the introduction of high-resolution esophageal manometry (HRM), the diagnosis of esophageal motility disorders has improved and led to a new classification with the Chicago Classification, which has been modified several times in the last decade, most recently in 2021 with the Chicago Classification v4.0. Compared to the previous version 3.0, there are some important changes that are presented based on the most important esophageal motility disorders in everyday clinical practice.

[Therapy of esophageal motility disorders]. / Therapieoptionen von primären Motilitätsstörungen des Ösophagus.

Esophageal motility disorders are diseases in which there are malfunctions of the act of swallowing due to a change in neuromuscular structures. The main symptom is therefore dysphagia for solid and/or liquid foods, often accompanied by symptoms such as chest pain, regurgitation, heartburn, and weight loss. Esophageal manometry is the gold standard in diagnostics. Endoscopy and radiology serve to exclude inflammatory or malignant changes. With the introduction of high-resolution esophageal manometry (HRM), the diagnosis of esophageal motility disorders has improved and led to a new classification with the Chicago Classification, which has been modified several times in the last decade, most recently in 2020 with the Chicago Classification v4.0. Compared to the previous version 3.0, there are some important changes that are presented based on the most important esophageal motility disorders in everyday clinical practice.

GWAS meta-analysis of 16 790 patients with Barrett's oesophagus and oesophageal adenocarcinoma identifies 16 novel genetic risk loci and provides insights into disease aetiology beyond the single marker level.

OBJECTIVE: Oesophageal cancer (EC) is the sixth leading cause of cancer-related deaths. Oesophageal adenocarcinoma (EA), with Barrett's oesophagus (BE) as a precursor lesion, is the most prevalent EC subtype in the Western world. This study aims to contribute to better understand the genetic causes of BE/EA by leveraging genome wide association studies (GWAS), genetic correlation analyses and polygenic risk modelling. DESIGN: We combined data from previous GWAS with new cohorts, increasing the sample size to 16 790 BE/EA cases and 32 476 controls. We also carried out a transcriptome wide association study (TWAS) using expression data from disease-relevant tissues to identify BE/EA candidate genes. To investigate the relationship with reported BE/EA risk factors, a linkage disequilibrium score regression (LDSR) analysis was performed. BE/EA risk models were developed combining clinical/lifestyle risk factors with polygenic risk scores (PRS) derived from the GWAS meta-analysis. RESULTS: The GWAS meta-analysis identified 27 BE and/or EA risk loci, 11 of which were novel. The TWAS identified promising BE/EA candidate genes at seven GWAS loci and at five additional risk loci. The LDSR analysis led to the identification of novel genetic correlations and pointed to differences in BE and EA aetiology. Gastro-oesophageal reflux disease appeared to contribute stronger to the metaplastic BE transformation than to EA development. Finally, combining PRS with BE/EA risk factors improved the performance of the risk models. CONCLUSION: Our findings provide further insights into BE/EA aetiology and its relationship to risk factors. The results lay the foundation for future follow-up studies to identify underlying disease mechanisms and improving risk prediction.

Influence of oral premedication and prewarming on core temperature of cardiac surgical patients: a prospective, randomized, controlled trial.

BACKGROUND: Perioperative hypothermia is still very common and associated with numerous adverse effects. The effects of benzodiazepines, administered as premedication, on thermoregulation have been studied with conflicting results. We investigated the hypotheses that premedication with flunitrazepam would lower the preoperative core temperature and that prewarming could attenuate this effect. METHODS: After approval by the local research ethics committee 50 adult cardiac surgical patients were included in this prospective, randomized, controlled, single-centre study with two parallel groups in a university hospital setting. Core temperature was measured using a continuous, non-invasive zero-heat flux thermometer from 30 min before administration of the oral premedication until beginning of surgery. An equal number of patients was randomly allocated via a computer-generated list assigning them to either prewarming or control group using the sealed envelope method for blinding. The intervention itself could not be blinded. In the prewarming group patients received active prewarming using an underbody forced-air warming blanket. The data were analysed using Student's t-test, Mann-Whitney U-test and Fisher's exact test. RESULTS: Of the randomized 25 patients per group 24 patients per group could be analysed. Initial core temperature was 36.7 ± 0.2 °C and dropped significantly after oral premedication to 36.5 ± 0.3 °C when the patients were leaving the ward and to 36.4 ± 0.3 °C before induction of anaesthesia. The patients of the prewarming group had a significantly higher core temperature at the beginning of surgery (35.8 ± 0.4 °C vs. 35.5 ± 0.5 °C, p = 0.027), although core temperature at induction of anaesthesia was comparable. Despite prewarming, core temperature did not reach baseline level prior to premedication (36.7 ± 0.2 °C). CONCLUSIONS: Oral premedication with benzodiazepines on the ward lowered core temperature significantly at arrival in the operating room. This drop in core temperature cannot be offset by a short period of active prewarming. TRIAL REGISTRATION: This trial was prospectively registered with the German registry of clinical trials under the trial number DRKS00005790 on 20th February 2014.

Clinical value of the Integrated Pulmonary Index® during sedation for interventional upper GI-endoscopy: A randomized, prospective tri-center study.

BACKGROUND AND STUDY AIMS: The Integrated Pulmonary Index® (IPI) is a mathematically-determined factor based on parameters of capnography and pulse oximetry, which should enable sensitive detection of impaired respiratory function. Aim was to investigate whether an additional measurement of the IPI during sedation for interventional endoscopy, compared to standard monitoring alone, allows a reduction of sedation-related respiratory depression. PATIENTS AND METHODS: 170 patients with standard monitoring randomly underwent either a blinded recording of capnography (control group, n=87) or capnography, including automated IPI calculation (IPI group, n=83), during deep sedation with midazolam and propofol. The primary endpoint was the maximum decrease of oxygen saturation from the baseline level before sedation. Secondary endpoints: incidence of hypoxemia (SaO2<90%), other sedation-related complications (apnea rate, bradycardia, hypotension), patient cooperation and satisfaction (VAS). RESULTS: Mean propofol dose in the IPI group (245±61mg) was comparable to the control group (225±47mg). The average drop of the oxygen saturation in the IPI group (6.5±4.1%) was nearly identical to that of the control group (7.1±4.6%, p=0.44). Apnea episodes >15s was found in 46 patients of the control and 31 of the IPI group (p<0.05). Frequency of occurrence of a drop in pO2-saturation <90%, bradycardia <50/min or a drop of systolic pressure <90mmHg were not significantly different in both groups. Mechanical ventilation was not required in any case. Patient cooperation and satisfaction were assessed similar in both groups. CONCLUSION: A clinically appealing advantage of IPI-assessment during deep sedation with midazolam and propofol for interventional endoscopy could not be documented. However, IPI registration was more effective in reducing the incidence of apnea episodes.

Nano-hydroxyapatite-coated metal-ceramic composite of iron-tricalcium phosphate: Improving the surface wettability, adhesion and proliferation of mesenchymal stem cells in vitro.

Thin radio-frequency magnetron sputter deposited nano-hydroxyapatite (HA) films were prepared on the surface of a Fe-tricalcium phosphate (Fe-TCP) bioceramic composite, which was obtained using a conventional powder injection moulding technique. The obtained nano-hydroxyapatite coated Fe-TCP biocomposites (nano-HA-Fe-TCP) were studied with respect to their chemical and phase composition, surface morphology, water contact angle, surface free energy and hysteresis. The deposition process resulted in a homogeneous, single-phase HA coating. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells (hMSCs) was studied using biological short-term tests in vitro. The surface of the uncoated Fe-TCP bioceramic composite showed an initial cell attachment after 24h of seeding, but adhesion, proliferation and growth did not persist during 14 days of culture. However, the HA-Fe-TCP surfaces allowed cell adhesion, and proliferation during 14 days. The deposition of the nano-HA films on the Fe-TCP surface resulted in higher surface energy, improved hydrophilicity and biocompatibility compared with the surface of the uncoated Fe-TCP. Furthermore, it is suggested that an increase in the polar component of the surface energy was responsible for the enhanced cell adhesion and proliferation in the case of the nano-HA-Fe-TCP biocomposites.

Oculopharyngeal muscular dystrophy as a rare cause of dysphagia.

Oculopharyngeal muscular dystrophy (OPMD) is a rare cause for late-onset dysphagia. OPMD normally follows an autosomal dominant inheritance. Herein we describe a rare case of an autosomal recessive inheritance of OPMD. An 80-year-old male presented with progressive dysphagia, frequent aspiration and change of voice getting inarticulate and hoarse. Physical examination showed ptosis of the right eyelid. Endoscopic and manometric investigation revealed a nonspecific motility disorder with hypopharyngeal esophageal hypotension. The severity of dysphagia became apparent when significant aspiration occurred during a barium swallow. Magnetic resonance imaging of the head ruled out a malignant or cerebral ischemic process. Based on the neurological examination, neurogenic muscular dystrophy was suspected and DNA analysis was performed. The analysis confirmed the extremely rare diagnosis of an autosomal recessive inheritance pattern of OPMD with homozygous (GCN)6(GCN)4(GCN) expansion of the poly-(A) binding protein nuclear 1 gene. As OPMD normally follows an autosomal dominant inheritance, consanguinity of the patient's parents was suspected.

Prospective evaluation of the routine use of a nasopharyngeal airway (Wendl Tube) during endoscopic propofol-based sedation.

BACKGROUND/AIMS: Insertion of a nasopharyngeal airway (NPA) during endoscopic sedation is only recommended in the event of respiratory problems. We evaluated the safety and efficacy of routine insertion of an NPA during sedation in gastrointestinal (GI) endoscopy. METHODS: Between July 2009 and April 2012, patients with colonoscopy or expected longer-lasting or therapeutic upper GI endoscopy were pseudo-randomized in a weekly alternating fashion to perform sedation (midazolam in combination with propofol) with or without NPA insertion. The primary outcome measure was respiratory depression (oxygen saturation <90%). Secondary measures included hypotension (systolic blood pressure <90 mm Hg), bradycardia (heart rate <40 beats/min) or nasopharyngeal damage after NPA insertion. RESULTS: 216 (106 females, mean age 60.7 ± 9.65 years) were enrolled. Colonoscopy was performed in 131 patients and upper endoscopy in 85 patients. In 105 patients an NPA was used (intervention group). Five (4.7%) of those patients showed minor nasopharyngeal injury. Respiratory depression (13.5 vs. 1.9%, p = 0.002) and hypotension (11 vs. 5%, p = 0.09) occurred more frequently in the control than in the intervention group. CONCLUSION: The routine placement of an NPA can reduce the frequency of hypoxemic events during endoscopic sedation with minor risks for nasopharyngeal injury.

Murine genetic deficiency of neuronal nitric oxide synthase (nNOS(-/-) ) and interstitial cells of Cajal (W/W(v) ): Implications for achalasia?

BACKGROUND AND AIM: Nitric oxide (NO) is an important inhibitory mediator of esophageal function, and its lack leads to typical features of achalasia. In contrast, the role of intramuscular interstitial cells of Cajal (ICC-IM) and vasoactive intestinal peptide (VIP) in lower esophageal sphincter (LES) function is still controversial. Therefore, we examined the function and morphology of the LES in vivo in NO-deficient (nNOS(-/-) ), ICC-IM-deficient (W/W(v) )-, and wild-type (WT) mice. METHODS: Esophageal manometry was performed with a micro-sized transducer catheter to quantify LES pressure, swallow evoked LES relaxation, and esophageal body motility. The LES morphology was examined by semiquantitative analysis of the immunoreactivity (reduction grade I-IV) of neuronal NOS (nNOS), ICC-IM, and VIP and their correlation with esophageal function. RESULTS: nNOS(-/-) in comparison to WT mice showed a significantly higher LES mean resting pressure with an impaired swallow induced relaxation, whereas W/W(v) mice had a hypotensive LES with decreased relaxation. W/W(v) and nNOS(-/-) mice demonstrated differing degrees of tubular esophageal dysfunction. The reduced immunoreactivity of nNOS correlated with an increased LES pressure and decreased LES relaxation, respectively. Cajal-cell reduction correlated with impaired LES relaxation, whereas VIP reduction revealed no correlation with esophageal function. CONCLUSIONS: The reduction of ICC-IM and nNOS can cause dysfunction of the LES and esophageal peristalsis, whereas VIP reduction seems to have no effect. ICC-IM and nNOS deficiency might be independent relevant causes of esophageal dysfunction similar to that seen in human achalasia.

Endoscopic approach to achalasia.

Achalasia is a primary esophageal motor disorder. The etiology is still unknown and therefore all treatment options are strictly palliative with the intention to weaken the lower esophageal sphincter (LES). Current established endoscopic therapeutic options include pneumatic dilation (PD) or botulinum toxin injection. Both treatment approaches have an excellent symptomatic short term effect, and lead to a reduction of LES pressure. However, the long term success of botulinum toxin (BT) injection is poor with symptom recurrence in more than 50% of the patients after 12 mo and in nearly 100% of the patients after 24 mo, which commonly requires repeat injections. In contrast, after a single PD 40%-60% of the patients remain asymptomatic for ≥ 10 years. Repeated on demand PD might become necessary and long term remission can be achieved with this approach in up to 90% of these patients. The main positive predictors for a symptomatic response to PD are an age > 40 years, a LES-pressure reduction to < 15 mmHg and/or an improved radiological esophageal clearance post-PD. However PD has a significant risk for esophageal perforation, which occurs in about 2%-3% of cases. In randomized, controlled studies BT injection was inferior to PD and surgical cardiomyotomy, whereas the efficacy of PD, in patients > 40 years, was nearly equivalent to surgery. A new promising technique might be peroral endoscopic myotomy, although long term results are needed and practicability as well as safety issues must be considered. Treatment with a temporary self expanding stent has been reported with favorable outcomes, but the data are all from one study group and must be confirmed by others before definite recommendations can be made. In addition to its use as a therapeutic tool, endoscopy also plays an important role in the diagnosis and surveillance of patients with achalasia.

Achalasia--a disease of unknown cause that is often diagnosed too late.

INTRODUCTION: Many physicians are inadequately familiar with the clinical features of achalasia. Often, it is not diagnosed until years after the symptoms arise. This is unfortunate, because a delay in diagnosis worsens the prognosis. METHODS: Selective review of the literature. RESULTS: Achalasia has a lifetime prevalence of 1:10 000. It is a neurodegenerative disorder in which the neurons of the myenteric plexus are lost, leading to dysfunction of the lower esophageal sphincter and to a derangement of esophageal peristalsis. In the final stage of achalasia, esophageal motility is irreversibly impaired, and complications ensue because of the retention of food that is no longer transported into the stomach. Aspiration causes pulmonary disturbances in up to half of all patients with achalasia. There may also be inflammation of the esophageal mucosa (retention esophagitis); this, in turn, is a risk factor for esophageal cancer, which arises in 4% to 6% of patients. The cause of achalasia is not fully known, but autoimmune processes appear to be involved in patients with a genetic susceptibility to the disease. CONCLUSION: Achalasia should be diagnosed as early as possible, so that complications can be prevented. In addition, guidelines should be established for cancer prevention in achalasia patients. Currently ongoing studies of the molecular causes of achalasia will probably help us understand its pathophysiology.

How best to approach endoscopic sedation?

Sedation is the drug-induced reduction of a patient's consciousness. The aim of sedation in endoscopic procedures is to increase the patient's comfort and to improve endoscopic performance, especially in therapeutic procedures. The most commonly used sedation regimen for conscious sedation in gastrointestinal endoscopy is still the combination of benzodiazepines with opioids. However, the use of propofol has increased enormously in the past decade and several studies show advantages of propofol over the traditional regimes in terms of faster recovery time. It is important to be aware that the complication rate of endoscopies increases when sedation is used; therefore, a thorough risk evaluation before the procedure and monitoring during the procedure must be performed. In addition, properly trained staff and emergency equipment should be available. The best approach to sedation in endoscopy is to choose a sedation regimen for the individual patient, tailored according to the clinical risk assessment and the anxiety level of the patient, as well as to the type of planned endoscopic procedure.

A small molecule binding to the coactivator CREB-binding protein blocks apoptosis in cardiomyocytes.

As a master transcription factor in cellular responses to external stress, tumor suppressor p53 is tightly regulated. Excessive p53 activity during myocardial ischemia causes irreversible cellular injury and cardiomyocyte death. p53 activation is dependent on lysine acetylation by the lysine acetyltransferase and transcriptional coactivator CREB-binding protein (CBP) and on acetylation-directed CBP recruitment for p53 target gene expression. Here, we report a small molecule ischemin, developed with a structure-guided approach to inhibit the acetyl-lysine binding activity of the bromodomain of CBP. We show that ischemin alters post-translational modifications on p53 and histones, inhibits p53 interaction with CBP and transcriptional activity in cells, and prevents apoptosis in ischemic cardiomyocytes. Our study suggests small molecule modulation of acetylation-mediated interactions in gene transcription as a new approach to therapeutic interventions of human disorders such as myocardial ischemia.

Electron microscopic studies of esophageal wall structures in patients with achalasia: casting more light on unresolved aspects of pathogenesis.

BACKGROUND/AIMS: Previous investigations of esophageal tissue and serum probes failed to identify a common etiologic agent predisposing to, triggering or causing achalasia. In order to further examine the detailed pathologic processes resulting in achalasia we performed electron-microscopic studies of muscle biopsies taken from the LES high pressure zone in patients undergoing surgery--either Heller myotomy or esophageal resection. METHODOLOGY: Smooth muscle biopsies with a 20 x 15-mm longitudinal segment of the myenteric plexus from the distal esophagus (lower border of the esophageal incision) in patients undergoing Heller myotomy for achalasia were taken. In patients with end-stage achalasia and mega-esophagus with esophageal resection, the complete esophageal body was available. For electron microscopy, ultrathin sections were contrasted with uranyl-acetate and plumbic citrate. The photographs were taken by a digitalized electron-microscope (ZEISS, Leo 905). RESULTS: A striking finding was the large number of mast cells in the region of the smooth muscle layers as well as in the surrounding connective tissue and also in close vicinity to the nerve cells and to the nerve fibres. The smooth muscle cells in these regions were very often stained less intensively, and they showed signs of an acute degenerative process. CONCLUSION: Our electron microscopic studies suggest that mast cells may play an important role in the secondary pathogenesis of achalasia. Esophageal retention and bacterial overgrowth with stasis esophagitis causing mucosal injury may be a mechanism of increased antigen exposure.

Low expression of chemokine receptor CCR5 in human colorectal cancer correlates with lymphatic dissemination and reduced CD8+ T-cell infiltration.

BACKGROUND: Chemokines and their receptors have been proposed to distinctly contribute to tumor growth, dissemination, and local immune escape. The aim of this study was to evaluate the relevance of the chemokine receptor CCR5 expression for the progression of human colorectal cancer. METHODS: CCR5 expression was assessed by RT-PCR analysis in 103 colorectal cancer patients. Intensity of CCR5 expression was correlated with both tumor and patient characteristics. Infiltration of tumor margins with CD8(+) T cells in the context of CCR5 expression was analyzed by immunohistochemistry in additional 18 colorectal cancer specimens. RESULTS: Human colorectal cancer revealed variable intensities of CCR5 expression ranging from absent (48/103: 47%), weak (30/103: 29%), intermediate (13/103: 13%), to strong (12/103: 12%). Absent or weak CCR5 expression was significantly associated with advanced UICC stages (P=0.02) and lymphatic metastasis (P=0.05). In addition, CCR5 expression positively correlated with CD8(+) T-cell infiltration in tumor margins (P=0.001). CONCLUSION: In summary, intermediate and strong CCR5 expression was significantly associated with nonmetastatic colorectal cancer and increased CD8(+) T-cell infiltration.

Labeling of human mesenchymal stromal cells with superparamagnetic iron oxide leads to a decrease in migration capacity and colony formation ability.

BACKGROUND AIMS: Labeling of stem cells is crucial to allow tracking of stem cell homing and engraftment after transplantation. In this study we evaluated the influence of cell labeling procedures using clinically approved small particles of iron oxide (SPIO) with or without transfection reagents (TA) on functional parameters of human mesenchymal stem cells (MSC). METHODS: The study was approved by the institutional review board of the University of Tubingen, Germany. Seven populations of bone marrow (BM)-derived human mesenchymal stem cells (MSC) were labeled with SPIO alone or in combination with various TA. Directly after labeling and two passages after labeling migration assays, quantification of colony-forming units and quantitative evaluation of the differentiation potential were performed. Quantification of the cellular total iron load (TIL), determination of the cellular viability and electron microscopy were also performed. RESULTS: Labeling of mesenchymal stem cells with SPIO with or without TA did not affect cell viability and differentiation potential significantly. SPIO in combination with TA coated the cellular surface directly after labeling but was incorporated into the cells after two passages. Labeling of mesenchymal stem cells with TA led to a significant decrease of migration capacity. This effect was abolished after two passages. Labeling with and without TA led to a significant decrease in colony formation ability. This effect could also be observed after two passages. CONCLUSIONS: The observed decrease of migration capacity and colony-formation ability was not associated with either TIL or localization of particles of iron oxide. SPIO labeling with and without TA had functional effects on human mesenchymal stem cells by decreasing the migration capacity and colony-formation ability of the stem cells.

New insights into the catalytic activation of the MAPK phosphatase PAC-1 induced by its substrate MAPK ERK2 binding.

PAC-1 is an inducible, nuclear-specific, dual-specificity mitogen-activated protein (MAP) kinase phosphatase that has been shown recently to be a transcription target of the human tumor-suppressor protein p53 in signaling apoptosis and growth suppression. However, its substrate specificity and regulation of catalytic activity thus far remain elusive. Here, we report in vitro characterization of PAC-1 phosphatase activity with three distinct MAP kinase subfamilies. We show that the recombinant PAC-1 exists in a virtually inactive state when alone in vitro, and dephosphorylates extracellular signal-regulated kinase 2 (ERK2) but not p38alpha or c-Jun NH(2)-terminal kinase 2 (JNK2). ERK2 dephosphorylation by PAC-1 requires association of its amino-terminal domain with ERK2 that results in catalytic activation of the phosphatase. p38alpha also interacts with but does not activate PAC-1, whereas JNK2 does not bind to or cause catalytic activation by PAC-1. Moreover, our structure-based analysis reveals that individual mutation of the conserved Arg294 and Arg295 that likely comprise the phosphothreonine-binding pocket in PAC-1 to either alanine or lysine results in a nearly complete loss of its phosphatase activity even in the presence of ERK2. These results suggest that Arg294 and Arg295 play an important role in PAC-1 catalytic activation induced by ERK2 binding.