1
|
Koester SW, Bishay AE, Lyons AT, Lu VM, Naik A, Graffeo CS, Levi AD, Komotar RJ. Recent Trends in Successful Neurosurgery Resident Matriculation: A Retrospective and Bibliometric Analysis. World Neurosurg 2024; 184:227-235.e1. [PMID: 38065356 DOI: 10.1016/j.wneu.2023.11.152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 11/29/2023] [Indexed: 02/19/2024]
Abstract
BACKGROUND Prior literature has demonstrated barriers to successful residency matching, including sex, medical school background, and international medical graduate status. Our aim is to characterize the recent trends in successfully-matched residents, with particular attention to geography and academic productivity. METHODS Resident information, including demographics and educational background, was gathered from program websites. Bibliometric analysis focused on PubMed publications from the top neurosurgery journals. A top 20 medical school was defined using the US News Rankings for research in 2022. Regression analyses were performed to explore the associations between total and first-author publications and other relevant factors, correcting for graduate studies. RESULTS A total of 114 institutions and 946 residents were included in the final analysis. Of the 845 with medical school information, 62 (7.3%) completed medical school internationally and 181 of 783 (23.1%) came from a top 20 medical school. Male residents had a higher proportion of residents with international undergraduate and international medical school degrees when compared to female residents [32 (7.5%) vs. 4 (2.4%), P = 0.021; 52 (8.6%) vs. 10 (4.2%), P = 0.026; respectively]. The multivariate regression analysis demonstrated a significant increase in publications for international medical school graduates (B = 8.3, P < 0.001), top tier medical school graduate (B = 1.3, P = 0.022), and male sex (B = 1.20, P = 0.019) for total number of publications. CONCLUSIONS Geographical factors, reported sex, and graduation status have influenced how resident candidates are perceived. Understanding these trends is vital for future resident matching. Addressing gender and educational diversity is essential to foster inclusivity and research-driven environments in neurosurgery residency programs.
Collapse
Affiliation(s)
- Stefan W Koester
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
| | - Anthony E Bishay
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Victor M Lu
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| | - Anant Naik
- Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Champaign, Illinois, USA
| | | | - Allan D Levi
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| | - Ricardo J Komotar
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| |
Collapse
|
2
|
Bishay AE, Lyons AT, Koester SW, Paulo DL, Liles C, Dambrino RJ, Feldman MJ, Ball TJ, Bick SK, Englot DJ, Chambless LB. Global Economic Evaluation of the Reported Costs of Deep Brain Stimulation. Stereotact Funct Neurosurg 2024:1-17. [PMID: 38513625 DOI: 10.1159/000537865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 02/13/2024] [Indexed: 03/23/2024]
Abstract
INTRODUCTION Despite the known benefits of deep brain stimulation (DBS), the cost of the procedure can limit access and can vary widely. Our aim was to conduct a systematic review of the reported costs associated with DBS, as well as the variability in reporting cost-associated factors to ultimately increase patient access to this therapy. METHODS A systematic review of the literature for cost of DBS treatment was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Embase databases were queried. Olsen & Associates (OANDA) was used to convert all reported rates to USD. Cost was corrected for inflation using the US Bureau of Labor Statistics Inflation Calculator, correcting to April 2022. RESULTS Twenty-six articles on the cost of DBS surgery from 2001 to 2021 were included. The median number of patients across studies was 193, the mean reported age was 60.5 ± 5.6 years, and median female prevalence was 38.9%. The inflation- and currency-adjusted mean cost of the DBS device was USD 21,496.07 ± USD 8,944.16, the cost of surgery alone was USD 14,685.22 ± USD 8,479.66, the total cost of surgery was USD 40,942.85 ± USD 17,987.43, and the total cost of treatment until 1 year of follow-up was USD 47,632.27 ± USD 23,067.08. There were no differences in costs observed across surgical indication or country. CONCLUSION Our report describes the large variation in DBS costs and the manner of reporting costs. The current lack of standardization impedes productive discourse as comparisons are hindered by both geographic and chronological variations. Emphasis should be put on standardized reporting and analysis of reimbursement costs to better assess the variability of DBS-associated costs in order to make this procedure more cost-effective and address areas for improvement to increase patient access to DBS.
Collapse
Affiliation(s)
- Anthony E Bishay
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Stefan W Koester
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Danika L Paulo
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Campbell Liles
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Robert J Dambrino
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Michael J Feldman
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Tyler J Ball
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Sarah K Bick
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Dario J Englot
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Lola B Chambless
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| |
Collapse
|
3
|
Jonzzon S, Chanbour H, Johnson GW, Chen JW, Metcalf T, Lyons AT, Younus I, Liles C, Abtahi AM, Stephens BF, Zuckerman SL. Who Can Be Discharged Home after Adult Spinal Deformity Surgery? J Clin Med 2024; 13:1340. [PMID: 38592140 PMCID: PMC10932028 DOI: 10.3390/jcm13051340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/16/2024] [Accepted: 02/21/2024] [Indexed: 04/10/2024] Open
Abstract
Introduction: After adult spinal deformity (ASD) surgery, patients often require postoperative rehabilitation at an inpatient rehabilitation (IPR) center or a skilled nursing facility (SNF). However, home discharge is often preferred by patients and hsas been shown to decrease costs. In a cohort of patients undergoing ASD surgery, we sought to (1) report the incidence of discharge to home, (2) determine the factors significantly associated with discharge to home in the form of a simple scoring system, and (3) evaluate the impact of discharge disposition on patient-reported outcome measures (PROMs). Methods: A single-institution, retrospective cohort study was undertaken for patients undergoing ASD surgery from 2009 to 2021. Inclusion criteria were ≥ 5-level fusion, sagittal/coronal deformity, and at least 2-year follow-up. Exposure variables included preoperative, perioperative, and radiographic data. The primary outcome was discharge status (dichotomized as home vs. IPR/SNF). Secondary outcomes included PROMs, such as the numeric rating scales (NRSs) for back and leg pain, the Oswestry Disability Index (ODI), and EQ-5D. A subanalysis comparing IPR to SNF discharge was conducted. Univariate analysis was performed. Results: Of 221 patients undergoing ASD surgery with a mean age of 63.6 ± 17.6, 112 (50.6%) were discharged home, 71 (32.2%) were discharged to an IPR center, and 38 (17.2%) were discharged to an SNF. Patients discharged home were significantly younger (55.7 ± 20.1 vs. 71.8 ± 9.1, p < 0.001), had lower rate of 2+ comorbidities (38.4% vs. 45.0%, p = 0.001), and had less hypertension (57.1% vs. 75.2%, p = 0.005). Perioperatively, patients who were discharged home had significantly fewer levels instrumented (10.0 ± 3.0 vs. 11.0 ± 3.4 levels, p = 0.030), shorter operative times (381.4 ± 139.9 vs. 461.6 ± 149.8 mins, p < 0.001), less blood loss (1101.0 ± 977.8 vs. 1739.7 ± 1332.9 mL, p < 0.001), and shorter length of stay (5.4 ± 2.8 vs. 9.3 ± 13.9 days, p < 0.001). Radiographically, preoperative SVA (9.1 ± 6.5 vs. 5.2 ± 6.8 cm, p < 0.001), PT (27.5 ± 11.1° vs. 23.4 ± 10.8°, p = 0.031), and T1PA (28.9 ± 12.7° vs. 21.6 ± 13.6°, p < 0.001) were significantly higher in patients who were discharged to an IPR center/SNF. Additionally, the operating surgeon also significantly influenced the disposition status (p < 0.001). A scoring system of the listed factors was proposed and was validated using univariate logistic regression (OR = 1.55, 95%CI = 1.34-1.78, p < 0.001) and ROC analysis, which revealed a cutoff value of > 6 points as a predictor of non-home discharge (AUC = 0.75, 95%CI = 0.68-0.80, p < 0.001, sensitivity = 63.3%, specificity = 74.1%). The factors in the scoring system were age > 56, comorbidities ≥ 2, hypertension, TIL ≥ 10, operative time > 357 mins, EBL > 1200 mL, preop SVA > 6.6 cm, preop PT > 33.6°, and preop T1PA > 15°. When comparing IPR (n = 71) vs. SNF (n = 38), patients discharged to an SNF were significantly older (74.4 ± 8.6 vs. 70.4 ± 9.1, p = 0.029) and were more likely to be female (89.5% vs. 70.4%, p = 0.024). Conclusions: Approximately 50% of patients were discharged home after ASD surgery. A simple scoring system based on age > 56, comorbidities ≥ 2, hypertension, total instrumented levels ≥ 10, operative time > 357 mins, EBL > 1200 mL, preop SVA > 6.6 cm, preop PT > 33.6°, and preop T1PA > 15° was proposed to predict non-home discharge. These findings may help guide postoperative expectations and resource allocation after ASD surgery.
Collapse
Affiliation(s)
- Soren Jonzzon
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
| | - Hani Chanbour
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
| | - Graham W. Johnson
- School of Medicine, Vanderbilt University, Nashville, TN 37235, USA; (G.W.J.); (A.T.L.)
| | - Jeffrey W. Chen
- Department of Neurological Surgery, Baylor College of Medicine, Houston, TX 77030, USA;
| | - Tyler Metcalf
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA;
| | - Alexander T. Lyons
- School of Medicine, Vanderbilt University, Nashville, TN 37235, USA; (G.W.J.); (A.T.L.)
| | - Iyan Younus
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
| | - Campbell Liles
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
| | - Amir M. Abtahi
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA;
| | - Byron F. Stephens
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA;
| | - Scott L. Zuckerman
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (S.J.); (H.C.); (I.Y.); (C.L.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA;
| |
Collapse
|
4
|
Younus I, Chanbour H, Chen JW, Johnson GW, Metcalf T, Lyons AT, Jonzzon S, Liles C, Roth SG, Abtahi AM, Stephens BF, Zuckerman SL. Combined Anterior-Posterior vs. Posterior-Only Approach in Adult Spinal Deformity Surgery: Which Strategy Is Superior? J Clin Med 2024; 13:682. [PMID: 38337376 PMCID: PMC10856410 DOI: 10.3390/jcm13030682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/20/2024] [Accepted: 01/22/2024] [Indexed: 02/12/2024] Open
Abstract
Introduction: Whether a combined anterior-posterior (AP) approach offers additional benefits over the posterior-only (P) approach in adult spinal deformity (ASD) surgery remains unknown. In a cohort of patients undergoing ASD surgery, we compared the combined AP vs. the P-only approach in: (1) preoperative/perioperative variables, (2) radiographic measurements, and (3) postoperative outcomes. Methods: A single-institution, retrospective cohort study was performed for patients undergoing ASD surgery from 2009 to 2021. Inclusion criteria were ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. The primary exposure was the operative approach: a combined AP approach or P alone. Postoperative outcomes included mechanical complications, reoperation, and minimal clinically important difference (MCID), defined as 30% of patient-reported outcome measures (PROMs). Multivariable linear regression was controlled for age, BMI, and previous fusion. Results: Among 238 patients undergoing ASD surgery, 34 (14.3%) patients underwent the AP approach and 204 (85.7%) underwent the P-only approach. The AP group consisted mostly of anterior lumbar interbody fusion (ALIF) at L5/S1 (73.5%) and/or L4/L5 (38.0%). Preoperatively, the AP group had more previous fusions (64.7% vs. 28.9%, p < 0.001), higher pelvic tilt (PT) (29.6 ± 11.6° vs. 24.6 ± 11.4°, p = 0.037), higher T1 pelvic angle (T1PA) (31.8 ± 12.7° vs. 24.0 ± 13.9°, p = 0.003), less L1-S1 lordosis (-14.7 ± 28.4° vs. -24.3 ± 33.4°, p < 0.039), less L4-S1 lordosis (-25.4 ± 14.7° vs. 31.6 ± 15.5°, p = 0.042), and higher sagittal vertical axis (SVA) (102.6 ± 51.9 vs. 66.4 ± 71.2 mm, p = 0.005). Perioperatively, the AP approach had longer operative time (553.9 ± 177.4 vs. 397.4 ± 129.0 min, p < 0.001), more interbodies placed (100% vs. 17.6%, p < 0.001), and longer length of stay (8.4 ± 10.7 vs. 7.0 ± 9.6 days, p = 0.026). Radiographically, the AP group had more improvement in T1PA (13.4 ± 8.7° vs. 9.5 ± 8.6°, p = 0.005), L1-S1 lordosis (-14.3 ± 25.6° vs. -3.2 ± 20.2°, p < 0.001), L4-S1 lordosis (-4.7 ± 16.4° vs. 3.2 ± 13.7°, p = 0.008), and SVA (65.3 ± 44.8 vs. 44.8 ± 47.7 mm, p = 0.007). These outcomes remained statistically significant in the multivariable analysis controlling for age, BMI, and previous fusion. Postoperatively, no significant differences were found in mechanical complications, reoperations, or MCID of PROMs. Conclusions: Preoperatively, patients undergoing the combined anterior-posterior approach had higher PT, T1PA, and SVA and lower L1-S1 and L4-S1 lordosis than the posterior-only approach. Despite increased operative time and length of stay, the anterior-posterior approach provided greater sagittal correction without any difference in mechanical complications or PROMs.
Collapse
Affiliation(s)
- Iyan Younus
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
| | - Hani Chanbour
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
| | - Jeffrey W. Chen
- Department of Neurological Surgery, Baylor College of Medicine, Houston, TX 77030, USA;
| | - Graham W. Johnson
- School of Medicine, Vanderbilt University, Nashville, TN 37232, USA; (G.W.J.); (T.M.); (A.T.L.)
| | - Tyler Metcalf
- School of Medicine, Vanderbilt University, Nashville, TN 37232, USA; (G.W.J.); (T.M.); (A.T.L.)
| | - Alexander T. Lyons
- School of Medicine, Vanderbilt University, Nashville, TN 37232, USA; (G.W.J.); (T.M.); (A.T.L.)
| | - Soren Jonzzon
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
| | - Campbell Liles
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
| | - Steven G. Roth
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
| | - Amir M. Abtahi
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Byron F. Stephens
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Scott L. Zuckerman
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37212, USA; (I.Y.); (H.C.); (S.J.); (C.L.); (S.G.R.); (A.M.A.); (B.F.S.)
- Department of Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| |
Collapse
|
5
|
Koester SW, Bishay AE, Lyons AT, Lu VM, Naik A, Graffeo CS, Levi AD, Komotar RJ. The Neurosurgery Match: COVID-19 Comparison and Bibliometric Analysis. World Neurosurg 2023; 178:e13-e23. [PMID: 37270100 PMCID: PMC10278925 DOI: 10.1016/j.wneu.2023.05.093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 05/22/2023] [Accepted: 05/23/2023] [Indexed: 06/05/2023]
Abstract
BACKGROUND Because of the effect of COVID-19 on academic opportunities, as well as limitations on travel, away rotations and in-person interviews, COVID-19-related changes could impact the neurosurgical resident demographics. Our aim was to retrospectively review the demographics of the previous 4 years of neurosurgery residents, provide bibliometric analysis of successful applicants, and analyze for the effects of COVID-19 on the match cycle. METHODS All American Association of Neurological Surgeons' residency program websites were examined for a list of demographic characteristics for current postgraduate years 1 to 4. Gathered information included gender, undergraduate and medical institution and state, medical degree status, and prior graduate programs. RESULTS A total of 114 institutions and 946 residents were included in the final review. Most (676, or 71.5%) of the residents included in the analysis were male. Of the 783 who studied within the United States, 221 (28.2%) residents stayed within the same state of his or her medical school. Fewer residents (104 of 555, or 18.7%) stayed within the same state of his or her undergraduate school. Demographic information and geographic switching relative to medical school, undergraduate school, and hometown showed no significant changes between pre-COVID-19 and COVID-19-matched cohorts overall. The median number of publications per resident significantly increased for the COVID-19-matched cohort (median, 1; interquartile range [IQR], 0-4.75) when compared with the non-COVID-19-matched cohort (median, 1; IQR, 0-3, P = 0.004), as did first author publications (median, 1; IQR, 0-1 vs. median, 1; IQR, 0-1; P = 0.015), respectively. The number of residents matching into the same region in the Northeast relative to undergraduate degree was significantly greater after COVID-19 (56 [58%] versus 36 [42%], P = 0.026). The West demonstrated a significant increase in the mean number of total publications (4.0 ± 8.5 vs. 2.3 ± 4.2, P = 0.02) and first author publications (1.24 ± 2.33 vs. 0.68 ± 1.47, P = 0.02) after COVID-19, with the increase in first author publications being significant in a test of medians. CONCLUSIONS Herein we characterized the most recently matched neurosurgery applicants, paying particular attention to changes over time in relation to the onset of the pandemic. Apart from publication volume, characteristics of residents and geographical preferences did not change with the influence of COVID-19-induced changes in the application process.
Collapse
Affiliation(s)
- Stefan W Koester
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
| | - Anthony E Bishay
- Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Victor M Lu
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| | - Anant Naik
- Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Champaign, Illinois, USA
| | | | - Allan D Levi
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| | - Ricardo J Komotar
- Department of Neurological Surgery, University of Miami, Miami, Florida, USA
| |
Collapse
|
6
|
Tchan MC, Choy KJ, Mackay JP, Lyons AT, Bains NP, Weiss AS. Interfacial asparagine residues within an amide tetrad contribute to Max helix-loop-helix leucine zipper homodimer stability. J Biol Chem 2000; 275:37454-61. [PMID: 10978321 DOI: 10.1074/jbc.m004264200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor Max is the obligate dimerization partner of the Myc oncoprotein. The pivotal role of Max within the Myc regulatory network is dependent upon its ability to dimerize via the helix-loop-helix leucine zipper domain. The Max homodimer contains a tetrad of polar residues at the interface of the leucine zipper domain. A conserved interfacial Asn residue at an equivalent position in two other leucine zipper proteins has been shown to decrease homodimer stability. The unusual arrangement of this Gln-Asn/Gln'-Asn' tetrad prompted us to investigate whether Asn(92) plays a similar role in destabilizing the Max homodimer. This residue was sequentially replaced with aliphatic and charged residues. Thermal denaturation, redox time course and analytical ultracentrifugation studies show that the N92V mutation does not increase homodimer stability. Replacing this residue with negatively charged side chains in N92D and N92E destabilizes the mutant homodimer. Further replacement of Gln(91) indicated that H bonding between Gln(91) and Asn(92) residues is not significant to the stability of the native protein. These data collectively demonstrate the central role of Asn(92) in homodimer interactions. Molecular modelling studies illustrate the favorable packing of the native Asn residue at the dimer interface compared with that of the mutant Max peptides.
Collapse
Affiliation(s)
- M C Tchan
- Department of Biochemistry, University of Sydney, Sydney, New South Wales 2006, Australia
| | | | | | | | | | | |
Collapse
|